SEPTEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
Although for the present nothing very definite can be stated with regard to the hydrocarbons formed in the various addition reactions, it is of interest that 2,3-dimethylbutane has been identified in the isohexane fraction from every reaction so far examined. Furthermore, i t would appear that addition tends to take place through a methyl group rather than through a secondary or tertiary carbon atom of the isoparaffin. Thus propylene and isobutane give considerable amounts of 2,4-dimethylpentane, isobutene and isobutane of 2,2,4-trimetbylpentane, isobutene and isopentane of 2,2,5-trimethylhexane, and so on. Whether hydrocarbons formed by addition to the secondary and tertiary carbon atoms undergo isomerization under the conditions of the reaction is uncertain (cf. Ipatiev and von Grosse, 4).
1083
Acknowledgment We wish to thank the Chairman of the Anglo-Iranian Oil Company, Limited, for permission to publish these results.
Literature Cited (1) Birch, Dunstan, Fidler, Pim, and Tait, IND.ENQ.CHEM.,31,
884-91 (1939). (2) Birch, Dunstan, Fidler, Pim, and Tait, J . Inst. Petroleum Tech., 24,303-20 (1938). ( 3 ) Brooks, Cleaton, and Carter, J . Research Natl. Bur. Standards, 19,3 (1937). (4) Ipatiev and von Grosse, paper presented before A. C . 5. meeting, Rochester, 1937. ( 5 ) Ipatiev and Pines, J . Org. Chem., 1, 477 (1936). (6) Ormandy and Craven, J. Inst. Petroleum Tech., 13, 311, 844 (1927).
Production of Aviation Fuels by HighPressure Hvdrogenation J
The application of high-pressure hydrogenation to the production of aviation gasolines, blending agents, and 100-octane fuels is discussed. A typical aviation naphtha hydrogenation plant at conversions of 5075 per cent per pass yields 80-95 per cent of 75-78 octane hydrogenated naphtha having excellent stability, high lead susceptibility, low sulfur content, and good color. Hydrogenation of isobutylene dimer and isonormal butylene codimer increases octane number from 82-84 to 97-100. Tables showing laboratory inspection data and properties of hydrogenated fuels and polymers, and high-octane aviation fuels produced by blending hydrogenated products are included.
HE past few years have seen a rapidly increasing demand for supplies of aviation fuels of high quality. Air transport facilities have experienced rapid expansion in this country and abroad and with the expansion has come the development of aircraft capable of carrying greater pay loads and requiring increasing take-off power. Aircraft size has been increased so that planes of 35 tons and heavier are in current use. The average power plant has been enlarged fourfold within the past ten years, and the average cruising speed has been increased from 100 to 200 miles per hour. Cruising range has been extended so that transoceanic routes are now operated as commercial enterprises. The new developments which have imposed on modern aircraft the necessity for increased capacity, extended range, and higher speed have proceeded concurrently with engine and fuel research. The availability of suitable aviation naphthas has, until the past few years, been limited principally to the supply which could be obtained from the light fractions of a rela-
T
E. V. MURPHREE AND E. J. GOHR Standard Oil Development Company, New York, N. Y.
C. L. BROWN Standard Oil Company of Louisiana, Baton Rouge, La
tively few crude stocks. These selected naphthas possessed the stability, volatility, and antiknock properties requisite to aircraft fuels. The results of research directed toward expanding the available quantity of aviation fuels and toward improving the quality of existing fuels have led to the development of hydrogenation products which meet both requirements. Naphthas can be produced by high-pressure hydrogenation which are similar in stability and volatility to naphthas prepared by distillation of selected crudes and which possess antiknock properties superior in general to such natural naphthas. Synthetic polymers also can be hydrogenated under high pressure to yield high-octane-number blending agents which can be incorporated in natural or hydrogenated naphthas for the production of premium-grade aviation fuels of 100 octane number or above. The production of hydrogenated naphthas to augment the supply of natural fuels has been made possible by the development of new catalysts for high-pressure hydrogenation operations. These catalysts possess the property of converting petroleum oils boiling outside the naphtha range into lower boiling cyclic and branched-chain compounds which impart desirable high-octane values to the naphtha product. The catalysts are mechanically rugged, are resistant to poisoning by sulfur, and can be kept in continuous operation for a year or more. Hydrogenated codimer (produced by high-pressure hydrogenation of a mixture of octenes obtained by the interaction of isobutylene and normal butylene) and similar blending agents are produced by high-pressure hydrogenation operations resembling those used for aviation naphtha production. The catalysts employed differ in composition from
INDUSTRIAL AND ENGINEERING CHEMISTRY
1084
those used for naphtha production but possess similar mechanical strength, resistance to poisoning, and long life. The present paper describes the process for producing hydrogenated naphthas and the properties of the naphthas thus made, the process for hydrogenating codimer and other synthetic polymers and the properties of the hydrogenated
VOL. 31, NO. 9
light gaseous fractions, and the stabilized product is then fractionated to yield aviation naphtha and cycle stock. Caustic washing completes the treatment for production of a finished high-quality aviation naphtha. As the flow sheet indicates, the cycle stock is returned to the unit to obtain ultimate conversion to aviation naphtha.
FIGURE1. FLOWDIAGRAMOF AVIATIONNAPHTHA PRODUCTION BY
HIGH-PRESSUREHYDROGENATION
polymers, and the properties of fuels of 100 octane number and above, available from blends of hydrogenated naphthas with hydrogenated codimer. Some of the material given in this paper has been presented previously ( I , 9,3 ) . The present paper serves the purpose of bringing this material together and incorporating it with more recent information.
Production and Properties of Hydrogenated Aviation Naphthas The production of high-octane-number aviation fuels by hydrogenation is accomplished in equipment and by a materials flow basically the same as described in earlier publications ( 5 , 6 , 7 ) . An outline of such a flow scheme is given on Figure 1. The diagram represents a materials flow which is typical for that of the commercial-scale operations a t the Standard Oil Company of Louisiana and in other plants conducting high-pressure hydrogenation operations for naphtha production. OPERATION TO ULTIMATE YIELDOF AVIATION TABLEI. RECYCLE GASOLINE IN A COMMERICAL-SCALE HYDROGENATION PLANT 5eed Stock Gravity, A. P. I. Aniline point, ' F.
34.0 132
348 0.5 12.0 58.0 572
Aviation Naphtha Gravity, A. P. I. 66.3 Reid vapor pressure a t 100' F., lb./sq. in. 6.9 Color Saybolt i-30 Octade No., A. S. T. M.-C. F. R. 7 6 . 5 Sulfur, % 0.002 Copper dish gum, mg./100 cc, 0.7 Distillation: 109 Initial b. p . , O F. a t 149 F. 17.0 a t 167" F. 32.0
8
82: 2bt",.:
F.
The process can be employed on a once-through basis to yield an aviation naphtha and heavier fractions. As Figure 1 also shows, recycle gas is employed not only for addition to the materials entering the reaction chambers, but also forcooling purposes by direct injection into the ovens, thus preventing undesired overcracking of the oil feed. TABLE11. DISTRIBUTION OF PRODUCTS FROM LARGE-SCALE PLANT HYDROGENATION FEEDSTOCK Gravity, A. P. I. Aniline oint, ' F. Sulfur $, Distilfation ' F.: Initial b.'p.
2%
Over
34.0 132 0.128 348 390 423
Distillation,
O
F. (contd.):
Final b. p. Recovery, %
PRODUCTS Butane, propane, and lighter Excess hydropentane Aviation gasoline: Gravity ' A. P. I. 66.3 Distillation : Initial b. p., F. Color, &bolt 30 Reid vapor pressure, Ib./sq. in. 6.9 a t 149' F. % ' a t 167' F. A. 9. T. M. octane No.: Clear 76.5 a t 203' F Plus 1 cc. Pba/gal. 85.3 a t 2120 90.7 Final b. p., F. Plus 3 cc. Pb/gal. Cycle stock: Gravity, A. P. I. 44.2 Disti,llation, O F.: Initial b. p. Aniline point, F. 127 50% over Final b. p. a Tetraethyllead.
+
2
F,:
452 482 530 550 572 98.5*,
109 17.0 32.0 62.5 70.0. 272 283 326 472
70.0 272
As the flow diagram shows, fresh feed to the hydrogenation system mixes with cycle stock being returned to the unit, then with fresh and recycle hydrogen. The mixture of oil and gas is heat-exchanged with products from the catalyst chambers and, after being heated further in a fired coil, it passes to the reaction ovens. Cracking and hydrogenation take place in contact with the catalyst, and the hydrogenated materials leave the oven in a converted state. After heat exchange, the reaction products are freed of hydrogen in a high-pressure separator and are then released to a lower pressure. Stabilization is employed to remove the
The hydrogen used in the above process is generated by the reaction of steam and natural gas (4). A mixture of steam and natural gas is passed through a bank of parallel tubes containing catalyst heated to high temperature by direct firing. Hydrogen and carbon monoxide are formed as products of the reaction. Additional steam is added to the. mixture, and further reaction is conducted in a second stage a t lower temperature. In this stage carbon monoxide and steam react to form carbon dioxide and additional hydrogen. The products of reaction are cooled to remove water, and the mixture of carbon dioxide and hydrogen passes to temporary storage in a gas holder. From the holder it is piped to a compressor which raises it in several stages to about 2507
.
SEPTEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
1085
INDUSTRIAL AND ENGINEERING CHEMISTRY
1086
commercial scale a t the Standard Oil Company of Louisiana. This plant has been in continuous operation for one year without changing the catalyst, which still has satisfactory activity for further use. A feed stock consisting of 60 per cent fresh feed or more is charged to the plant, where it is processed for ultimate yield of aviation gasoline. The yields on fresh feed are about 85 per cent aviation gasoline plus approximately 20 per cent butanes and 8 per cent pentanes above that required to produce 7-pound Reid vapor pressure gasoline. The butanes and pentanes are largely present in the is0 form. Inspections of feed stock to this plant and the hydrogenated naphtha obtained are given in Table I. The conversion of feed stock into the various products is given in Table 11. A feed stock with a boiling range of 348-572' F. is converted to ultimate yield of a high-quality aviation naphtha. The naphtha possesses an octane number of 76.5, a color of +30 Saybolt, a sulfur content of 0.002 per cent, and copper dish gum of 0.7 mg. per 100 cc. A variety of feed stocks can be employed for production of hydrogenated aviation naphthas. Table I11 gives the inspections of aviation naphthas from four feed stocks investigated in experimental equipment. The feed stocks vary considerably in characteristics, ranging from 35.3 A. P. I. heavy naphtha to a 21.4' kerosene fraction. The resulting hydrogenated naphthas possess octane numbers of 75.8-78, and are of good volatility and stability. TABLE 111. HYDROGENATED AVIATION NAPHTHAS FROM FOUR FEED STOCKS
Feed stock: Gravity ' A. P. I. Sp, gr. dOo./6OoF. Aniline olnt, O F. Sulfur, Distillation, F.: Initial b. p.
Heavy Naphtha from Mirando Crude
Mirando Cracked Cycle Stock
35.3 0.8483 117 0.050
28.6 21.4 31.0 0.9254 0.8838 170 129 90 0.460 0.20 0.070
220 344 408 460 514
Final b. p. Hydrogenated aviation fuel: Gravity, A. P. I. 64.9 Color, Saybolt 4-30 Sulfur, yo 0.011 Acid heat, e F. 2 Reid va or pressure a t 100' F., 1b.Lc-l. in. 7.0 A. S. T. M.-C. F. R. octane No.: Clear 78.3 90.1 PIUS3 cc. Pb/gal. Distillation: a t 158' F. 26.0 D LQ a t 167O F. ' 35.3 a t 203" F. 63.5 D LQ a t 212O F. 72.5 Final b. p., F. 278
f
Q
D
+ +
+ L = distillate +
308 405 445 491 531
Kerosene Fraction from Coastal Crude
379 430 460 507 554
Gaa Oil from Venezuelan Crude
343 402 477 564 614
61.1 59.4 66.7 -I-30 4-30 0.002 +3&1 0.002 2 2 2 6.9
7.0
6.7
76.4 90.8
78.0 92.0
75.8 90.5
12.5 20.5 53.0 59.0 280
12.0 18.5 55.0 65.5 276
28.5 35.0 59.5 68.0 283
108s.
The usual specifications for aviation gasolines call for the following basic properties: high stability, satisfactory volatility, high octane rating, and freedom from impurities such as sulfur compounds. The stability requirements of aviation gasolines are necessarily rigid inasmuch as this type of fuel must be able to withstand various storage conditions for reasonably long periods of time without change in properties. I n respect to stability, hydrogenated fuel is similar to virgin aviation gasoline which, by experience, is known to be satisfactorily stable under widely differentstorage conditions. Typical inspections of hydrogenated aviation gasoline are compared in Table IV with similar inspections of a virgin aviation naphtha from one of the best crude sources. According to this comparison, the hydrogenated and virgin avia-
VOL. 31, NO. 9
TABLE IV. COMPARATIVE INSPECTIONS OF VIRGINAND HYDROGENATED AVIATION NAPHTHAS
Gravity O A. P. I. Color daybolt Doctdr test Copper dish corrosion Copper dish gum. ma./100 cc. U.9;Army g u m . British Air Ministry gum, mg./100 Existent Potential Sulfur, % Breakdown time, hr. Acid heat, O F. Bromine No., cg. Br/gram oil Water tolerance Freezing point F. Reid vapor prdssure a t loOD F., lb./ sq. In.
temp.,
Virgin Aviation Naphtha 68.8 +Ess
Pass 1.5 Nil
00.:
-."
1 Q
2.0 0.026 2;
+
Hydrogenated Aviation Naphtha from Large-Scale Operation 66.3 +Ess
Pass 0.1 Nil
0.8 1.0 0.005 2;
+
2 Pass < -76
2 Pass < -76
7.0
6.9
108 31.0 71.0 276 98.0 1.0 Neutral
109 32.0 68.5 272 99.0 1.0 Neutral
330
329
74.1 82.9 88.6 93.2 94.9 97.0
76.5 85.3 90.4 95.5 98.0 99.4
Clear 72.8 Plus 1 00. Pb/gal. 83.8 3 00. 90.2 .Plus 6 cc. 95.5 Plus 8 CO. 98.6 Plus 10 CC. 99.5 British Air Ministry octane No.: Clear 74.7 Plus 1 oc. Pb/gal. 82.6 Plus 3 00. 88.7 Plus 6 cc. 93.7 Equal t o pure isoijctane plus 0.07 cc. Pb/gal. b 2 cc. Pb/gal.
76.0 87.9 92.7 98.0 102.0
U.S. Army Air Corps octane No.: PIUS
76.5 85.9 90.5b 95.7
tion naphthas of approximately the same volatility show similar stability characteristics as indicated by breakdown time, Army gum, and copper dish gum values. Both gasolines show negligible olefin content as indicated by low bromine numbers and low acid heat values. Compared on the basis of accepted stability tests, the two gasolines are essentially alike. Clear (i. e., unleaded) octane ratings of hydrogenated aviation gasoline as determined by A. S. T. M.-C. F. R., Army Air Corps, and British Air Ministry methods of test (Table IV) are substantially higher than corresponding values obtained on virgin aviation fuel. I n this comparison the hydrogenated aviation fuel shows an advantage of about two points in octane rating over the natural gasoline (76.5 us. 74.2 A. S. T. M.-C. F. R.), but it is feasible to increase this differential by producing hydrogenated naphthas of 78 A. S. T. M.-C. F. R. clear octane ratings as illustrated by the results in Table 111. In view of current trends toward higher antiknock aviation fuels, the octane number advantage shown by the hydrogenated aviation fuel over the virgin gasoline becomes significant. Ability of present-day aviation fuel to show a high octane number response on additions of tetraethyllead is of importance commensurable with the clear octane rating. Aviation gasolines with octane ratings of 87 to 90 A. S. T. M.-C. F. R. are, in most instances, manufactured by additions of not more than 3 cc. of tetraethyllead in suitable base naphtha. It is therefore essential that the base gasoline have good response to tetraethyllead, in addition to a high clear octane rating. Hydrogenated aviation fuel is well suited for the
SEPTEMBER, 1939
loss
INDUSTRIAL AND ENGINEERING CHEMISTRY
CC.OF TETRAETHYL LEAD PER U.S.CAL.
FIGURE 2. INCREASE IN OCTANE RATINGON ADDITION OF TETRAETHYLLEAD TO HYDROGENATED AVIATIONGASOLINE
manufacture of fuels containing tetraethyllead, since i t possesses higher octane numbers both in the clear and leaded form than are commonly obtainable with the best virgin fuels. The high tetraethyllead response of hydrogenated fuel is illustrated by the lead curves for the A. S. T. M.-C. F. R. and Army Air Corps test methods given in Figure 2. I n these curves the Army test method gives increased leaded octane ratings over those obtainable by the A. S. T. M.-C. F. R. method. For example, with 8 cc. of tetraethyllead per gallon the octane rating by the A. S. T. M.-C. F. R. method is 98, which compares with a value of 100 by the U. S. Army Air Corps method. On the addition of 10 cc. of tetraethyllead per gallon the hydrogenated fuel attains an octane rating exceeding 100 (estimated 101.5) by the U. s. Army Air Corps method. The high incremental increase in octane ratings shown by the hydrogenated aviation fuel on additions tof tetraethyllead is possibly due in part to its freedom from
The virgin and the hydrogenated aviation fuels show sulfur contents well below the 0.10 per cent maximum specified by the United States Army. It is to be noted that the hydrogenated fuel shows the extremely low, sulfur content of 0.005 per cent. An examination of the properties of hydrogenated aviation fuel in comparisvn with those of aviation gasoline obtained from selected natural sources showed that the former has a decided advantage over the latter in respect to octane number and tetraethyllead susceptibility. This advantage of the hydrogenated fuel over the natural gasoline has been confirmed by tests in large-scale aviation motors, as well as in experimental motors operating under supercharged conditions. An investigation of the types of hydrocarbons present in hydrogenated aviation fuel has been made by distillation through a 75-plate fractionating column and subsequent analyses of narrow fractions. The curves in Figures 3 and 4 are illustrative for aviation fuel derived experimentally from virgin feed stock of a naphthenic type. By employing the refractive index in combination with extraction methods, as a relative measure of the types of hydrocarbons present in 2 per cent fractions from the gasoline, it is possible to generalize on the composition. The amount of normal paraffins appears to be small. Preponderant quantities of naphthenes and branched-chain paraffin hydrocarbons are shown to be pres-
ci
1.45
0 0
N
t X
4
1.41
W
2
+2
1.39
a a b 1.37
340
1.46
300
1.44
$ 260
1.42
-BEFORE EXTRACTION -- AFTER ACID EXTRACTION I
~
1
I
~
I
I
/
I
I
'
Y0
N
a
a
I3
2 X W
W
1.40
220
z
W
a
2
W
a
t-
3 + 180
1.38
2 a W LL
a 140
1.36
IO0
1.34
ent. Only a trace of cyclohexane is indicated, but a reasonably high percentage of methylcyclopentane is shown to be present. The aromatic content of the gasoline is indicated to be from 6 to 7 per cent. The molecular structure and saturated nature of the hydrocarbons account for the stability, octane rating, and lead susceptibility of the hydrogenated fuel.
PER CENT
FIGURE 3. TRUE-BOILING-POINT DISTILLATION CURVEON HYDROGENATED AVIATIONNAPHTHA WITH REFRACTIVE INDEX OF NARROW CUTS
impurities, such as sulfur or nitrogen compounds, as well as to its desirable chemical constitution. I n contrast with virgin aviation gasoline, the hydrogenated fuel shows the following per cent sulfur content: Hydrogenated aviation fuel Virgin aviation fuel U. S. Army speoificationa, max.
0.005 0.026
0.10
High-octane Blending Agents from Hydrogenation In addition to production of aviation naphthas, highpressure hydrogenation is currently employed on a commercial scale for,preparing high-octane-number blending agents. One of the principal blending agents thus made results from the hydrogenation of octenes available from copolymerization of is0 and normal butylenes. This type of hydrogenation can also be carried out a t low pressures (8). The low-pressure operation gives products and yields similar to the highpressure operation. From an economic standpoint the
INDUSTRIAL AND ENGINEERING CHEMISTRY
1088
VOL. 31, NO. 9
choice between the two operations for polymer hydrogenation depends upon the particular circumstances involved. The polymerization products or codimer prepared from the unsaturated compounds available in refinery gas are comparatively low in octane number (82-84) and are low in response to added tetraethyllead. Upon hydrogenation, however, the resulting saturated products have octane numbers in the range of 97 to 100 and in addition have a high lead susceptibility. The production of high-octane blending agents on a commercial scale has made available the means of preparing aviation fuels of the 100 octane-number range and higher. Commercial-scale hydrogenation of polymers a t the Standard Oil Company of Louisiana and in other plants is conducted in the same type of high-pressure equipment used for aviation naphtha production. A different catalyst than that used for aviation gasoline production is employed for hydrogenation of dimer. This catalyst also maintains its activity over a long period of time. A batch of catalyst currently in use a t the Baton Rouge plant has continued to operate a t satisfactory temperature level and has given about 100 volume per cent yield over a period of 8 months. The final product requires stabilization for the removal of a small amount of butane followed by a caustic wash which completes the treatment necessary to produce a finished material, Inspections of representative feed and product from commercial-scale operation are given in Table V. Hydrogenation of the codimer resulted in a product of negligible acid
TABLE V. COMMERCIAL-SCALE H.YDROGENATION OF CODIMER Gravity, A. P. I. Doctor test Copper dish corrosion Copper dish gum, mg./100 cc. Color Saybolt Reid $apor pressure at 100' F., Ib./sq. in. Sulfur, % Bromine No., cg. Br/gram oil Aniline point, O F. A. 8. T. M . 4 . F. R . octane No.
Codimer Feed Stock 60.7 Does not pass Pass 1.9
+Y.0 . 093 6 137 102 84.0
198 223 226 228 229 230 231 232 233 234 257 98.0
Hydrogenated Codimer 65.8 Pass Pass 0.3 +30 1.9 0,008 0.3 159 97.6 196 222 225 226 227 228 230 231 232 234 255 98.0
TABLE VI. HYDROGENATED ISOBUTYLENES Gravity, O A. P. I. Color, Saybolto Aniline oint, F. Sulfur, Doctor t i s t Copper dish corrosion Copper dish gum, mg./100 00. Acid heat, O F. Bromine No. Reid vapor pressure a t 100' F., lb./sq. in. A. 8. T. M . 4 . F. R. octane No. Distillation, F . : Initial b. p. 5% over 10
B
40
$?I%
b. p.
Reoovery, % Residue, %
Diisobutylene 71.2 +30 172 0.013 Pass
Pass
0.5 3 3 2.7 99.2
186 204 208 210 211 211 211 212 212 213 215 221 246 98.0 0.7
Triisobutvlene 53.6 4-30 179 0.012 Pass Pass 1.7
. 1. . . .
0.2 98.5 336 342 343 347 348 350 352 353 354 356 359 365 392 98.0 0.7
LABORATORY HIGH-PRESSURE EQUIPMENT IN THE DEVELOPMENT AND RESEARCH DEPARTMENT OF THE STANDARD OIL COMPANY OF LOUISIANA
heat, bromine number, and copper dish gum, which indicates a high stability to long-time storage. The octane number of the hydrogenated product is 97.6, compared with 84 on t h e feed. The hydrogenated codimer is not an aviation fuel of itself since it does not possess the boiling range desirable for standard engine use. The hydrogenated product is therefore principally employed as a blending agent to increase the octane number level of natural or hydrogenated aviation naphthas. The high octane number of the hydrogenated codimer, together with its natural stability, makes it particularly suitable for production of fuels of the 100 octane number range and higher. The hydrogenation process as described for production of hydrogenated codimer is also applicable to other polymer stocks. For example, hydrogenation of polymers composed mainly of diisobutylene gives a product with properties quite similar to those of hydrogenated codimer. The inspection of a representative product of this type is given in Table VI. The hydrogenated diisobutylene has an octane number of 100, and its over-all boiling range is somewhat lower than that of hydrogenated codimer. Hydrogenated diisobutylene is a blending agent somewhat superior in octane blending properties to hydrogenated codimer. The supply of diisobutylene which can be prepared from refinery unsaturates is much smaller, however, than the quantity of codimer which can be manufactured since in the latter case polymerization not only of isobutylene but also of normal butylenes takes place. The higher boiling fractions associated with diisobutylene can be hydrogenated to yield a product of 98 octane number. The inspection of such a trimer (triisobutylene) is given in Table VI. The hydrogenation of the higher boiling polymers. is accompanied by some decomposition to lower boiling products with consequent production of some octanes and butanes in the total product.
SEPTEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
Mixed polymers of propylene and butylenes are also readily hydrogenated. The octane numbers of hydrogenated products of this type have been found to be lower than those of hydrogenated butylene polymers, probably because of the occurrence of a higher proportion of straight-chain compounds in the material containing propylene.
Premium-Grade Aviation Fuels from Hydrogenated Naphthas and Hydrogenated Codimer Hydrogenated aviation naphtha and hydrogenated codimer afford a suitable combination for expanding the supplies of 100-octane fuels (fuels containing 3 cc. of tetraethyllead per gallon and meeting 100 octane number measured by the Army method of test). The employment of hydrogenated naphthas with octane numbers of 76 to 76.5 (A. S. T. M.-C. F. R.) displays a superiority over the use of virgin naphthas with octane numbers of 7 2 to 7 5 in that less hydrogenated codimer or other high-octane blending agent is required for 100-octane blends, with consequent increase in the supply of premium fuel that can be made from given volumes of blending agent. As a result of the relatively low volatility of hydrogenated codimer it is possible to extend its availability by adding to the blend of hydro codimer and aviation gasoline a naphtha of high volatility and high octane number. Among such high-volatility naphthas are isopentane, selected fractions of certain rirgin naphthas, and the excess pentane (largely isopentane) produced in the hydro operation. The inspections of a 100-octane aviation fuel prepared by blending hydrogenated aviation naphtha with hydrogenated codimer and light blending agent are given in Table VII. The blend meets the current specifications of the U. S. Army, British Air Ministry, and French Air Ministry for this grade of naphtha. It is to be noted that the sulfur content is low and the stability high as judged by the low gum value in the copper dish test (2.2 mg.) and the low acid heat (2' F.).
1089
lead contents, to give fuel grades intermediate between 76 and 100 octane number, and to give fuels with octane numbers above 100. Table VI11 lists the properties of two blends of 102 and 104 octane number. These blends meet the conventional specifications for volatility, sulfur, and stability. The high-octane blending agent referred to in Table VI11 consists of a mixture of hydrogenated codimer and isopentane. TABLE VIII. AVIATION FUELS O F 102 AND 104 OCTANE NUMBER PREPARED FROM HYDRO CODIMER BLENDING: AGENTAND HYDROQENATED AVIATION GASOLINE 102 Army Octane No. Fuel 69.5 Blue 2.0 Pass Pass 1 0.01
Gravity, A. P. I. Color Copper dish gum, mg./100 cc. Copper dish corrosion Doctor testo Acid heat, F. Sulfur, % Reid yapor pressure a t 100' F., lb./ s q . in. A. S. T. M. disiillation: Initial b. p., F. % a t 167" F. a t 212' %. Final b. p., F. Recovery % ' Sum of 16 50% distn. temp., O F. Tetraethyllead, cc./gal. A. S.T. M.-C. F. R. octane No. U. S. Army Air Corps octane No.
+
104 Arm Octane No. h e 1 69.4 Blue 1.9 Pass Pass 1 0.01
7.0
7.0
108 21.0 51.0 257 98.5 357 3.0 101.2 102.0
108 21.5 52.0 257 98.5 356 6.0 103.0 104.0
Aviation fuels of the 100-octane grade have rendered 8 significant contribution to the aircraft field by making available greater take-off capacity. With increased horsepower for the take-off, greater fuel supplies can be carried and the flight range of aircraft can be markedly increased. The increased take-off capacity can alternatively be used for handling increased pay loads. A steadily increasing demand for supplies of 100-octane fuel is to be expected in the future on the basis of the superior performance at a more economic level which can be obtained with these fuels. In addition to increasing TABLEVII. 100 ARMYOCTANE FUEL FROM HYDROGENATED demand for 100-octane fuels, it is to be expected that superAVIATION NAPHTHA, HYDROGENATED CODIMER, AND ISOPENTANEfuels above 100 in octane number will be called for as aircraft WITH 3.0 Cc. OF TETRAETHYLLEAD PER U. S. GALLON increase in size, power, and cruising range. As this paper inGravity, A. P. I. 68.8 dicates, high-pressure hydrogenation makes available inColor Blue Sulfur, % 0.004 creased supplies of base aviation naphthas and of the hydroDoctor test Pass genated polymers employed in the production of high-octane Copper dish corrosion Pass Copper dish gum, mg./100 cc. 2,2 fuels. Acid heat, ' F. 2 Reid vapor pressure at 100' F., lb./sq. in. 7.0 A. S. T. M.-C. F. R. octane No. 9 9 . 0 U. S. Army Air Corps octane N0.Q 100.5 a
Equal t o pure isodctane plus 0.02 cc. tetraethyllead per gallon.
I n addition to production of 100-octane fuels containing 3 cc. of tetraethyllead per gallon, hydrogenated naphthas and codimer can be blended to give 100 octane number with other
Literature Cited (1) Brown and Gohr, Proc. 3nd World Petroleum Congr., 2, 281-7
(1937). (2) Ibid., 2, 289-98 (1937). (3) Brown and Tilton, Oil Gas J.,36, No.46, 74 (1938). (4)Byrne, Gohr, and Haslam, IND.ENG.CHEM.,24, 1129 (1932). (5) Haslam and Russell, Ibid., 22, 1030 (1930). (6) Russell and Gohr, J . Inst. Petroleum Tech., 18,595 (1932). (7) Russell, Gohr, and Voorhies, Ibid., 21, 347 (1934). (8) Shell Development Co. and Shell Chemical Co., Proc. Am. Petroleum Inst., 8th Mid-Year Meeting, Sect. I I I , 19,87 (1938).
