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
May 1953
with that of 2-hydroxybenzylidenerhodanine (11-193). The chlorine atom, which as the sole substituent in the phenyl ring markedly increases the activity of benzylidene rhodanine in soil burial tests, is usable to raise the activity of 2-hydroxybenzylidenerhodanine. . Table VI1 gives data on the activity of some rhodanine derivatives of methyl aromatic ketones. I n these compounds, the hydrogen atom attached to the double-bonded carbon of the benzylidene group has been replaced by methyl. It is therefore logical to compare their activity with that of corresponding benzylidene derivatives. Thus VII-230 is the homolog of 1-159, VII-238 of V-209, VII-270 of VI-290, and VII-231 of VI-252. I n all cases the aldehyde derivative is more effective than the corresponding ketone derivative, but the order of activity of the latter roughly parallels that of the former. The work described in this paper was supported by a contract with the Army Chemical Corps. ACKNOWLEDGMENT
The authors express their appreciation to Elise N. Lawton and Marny Potter, who assisted in the testing and synthesis of compounds.
1033
LITERATURE CITED
(1) Bargellini, G., Oazz. chim. {tal., 36 11, 129 (1906). (2) Barltrop, J. A., J . Chem. SOC.,1946, 958. (3) Brown, F. C., Bradsher, C. K., Bond, S. M., and Potter, M., J . Am. Chem. Soc., 73, 2357 (1951). (4) Brown, F. C.,Bradsher, C. K., and Lawton, E. N., IND. ENG. CHEM.,45, 1027 (1953). (5) Brown, F. C.,Bradsher, C. X., McCallum, S. G., and Potter, M., J. Org. Chem., 15,174 (1950). (6) Campbell, N., and McKail, J., J. Chem. SOC.,1948, 1251. (7) Feigl, F.,2.anal. Chem., 74, 386 (1928). (8) Fisher, H. E., and Hibbert, H., J . Am. Chem. Soc., 69, 1208 (1947). (9)Goldsworthy, M. C.,and Gertler, S. I., PZant Disease Reptr., Suppl., 182, 89 (1949). (10) Horsfall, J. G., “Fungicides and Their Action,” pp. 154-5, Waltham, Mass., Chronica Botanica Co., 1945. (11) Julian, P. L., and Sturgis, B. M., J . Am. Chem. SOC.,57, 1126 (1935). (12) Kolthoff, I. M., Ibid.,52, 2222 (1930). (13) Nencki, M., Ber., 17, 2277 (1884). (14) Sachs, F.,and Michaelis, F., Ibzd., 39, 2163 (1906). ANAL.ED., (15) Scott, A. W.,and Robbins, T. E., IND.ENQ.CHEM., 14, 206 (1942). (16) Sugasawa, S.,and Shigehara, H., Ber., 74, 459 (1941). (17) Zentmyer, G.A., Science, 100,294 (1944), RECBIVED for review November 25, 1952.
A C C ~ P T EJanuary D 14, 1953.
Emulsified Ammonium Nitrate as an Ignition Accelerator ISRAEL CORNET AND ALEXANDER BOODBERG University of California, Berkeley, Calif.
T
HIS paper deals with theoretical and experimental aspects
*
of the use of emulsified ammonium nitrate solutions t o promote the ignition of hydrocarbon fuels. Ammoniumnitrate decomposes a t 210” C. (410‘ F.) ( 7 ) ;this reaction is spontaneous, exothermic, and releases nitrous oxide (18). The nitrous oxide can support combustion (a), or upon further heating it can decompose and release oxygen (8, 11). The nitrate ion and the nitric acid formed under some conditions when ammonium nitrate is heated ( l a ) , may act as oxidizing agents. It was shown by Lewis and Randall ( 9 ) that the decomposition into its elements of even aqueous solutions of ammonium nitrate will give negative values for changes of free energy and enthalpy; the recently published values differ somewhat from these values ( 7 , cf. 4, 9) but they are still of the same order of magnitude. As indicated by the equation given by Lewis and Randall (9)
NH4NOa ( 9 )
+Nz (g)
+ 2Hz0 (g) + ‘/zO~ (g) + heat
This net result of heating ammonium nitrate to high temperatures indicates that ammonium nitrate might act as an ignition accelerator. However, the insolubility of the salt in hydrocarbon fuels has prevented its use in “energizing” these fuels (6). There has been only an occasional reference in the literature to date to the use of emulsified ammonium nitrate solutions in fuels. The emulsified solutions were used with gasoline in an ordinary automobile engine (S),where the ammonium nitrate would act as an undesirable proknock agent. Because even aqueous solutions of ammonium nitrate are thermodynamically unstable (9),such solutions could conceivably be used to modify combustion in a furnace, a gas turbine, or an engine. During combustion the water in which the ammonium nitrate is dissolved will be vaporized; for dilute solutions, the latent heat of vaporization of the water will exceed the heat of
decomposition of the ammonium nitrate. Ammonium nitrate is not only highly soluble in water, but also relatively soluble in alcohols, acetone, and other media ( 7 ) . With modern emulsion technology, it would be feasible to utilize such additives t o fuels if their effects were desirable and economical. In this investigation, studies were conducted on the effect of emulsified aqueous ammonium nitrate on the ignition of a hydrocarbon fuel, a t atmospheric pressure, and on the performance of such emulsified fuel in a compression ignition engine. Comparisons were made with the hydrocarbon fuel, and with water emulsified in the hydrocarbon fuel. EXPERIMENTS AND RESULTS
Emulsion fuels are readily prepared; for these experiments a Diesel fuel containing 0.25% emulsifier was stirred in a Waring Blendor and either water or aqueous ammonium nitrate solutions were added dropwise. stirring was continued for a t least 5 minutes. The Diesel fuel used was a commercial California stock of specific gravity 0.8600 a t 80” F., and cetane number 39; the emulsifier used was “polyethylene glycol 400, di, tri ricinoleate” (supplied by the Glyoo Products Co., Inc.); the ammonium nitrate solutions were 5 N , specific gravity was 1.15 a t 60’ F. (A 5 N ammonium nitrate solution gives an endothermic reaction, as the vaporization of the water requires more heat than the decomposition of the ammonium nitrate releases.) Metered drops of the fuels were allowed to fall onto a heated quartz plate in a heated chamber at atmospheric pressure, and the time required for the drop to ignite was observed. Details on the atmospheric pressure apparatus used for this study of ignition delay are available (6). The results obtained in this ignition study are shown in Figure 1. There was an interesting difference in the ignition behaviors of the treated and untreated fuels. Diesel fuel drops spread on the heated quartz plate and then ignited relatively quietly with a puff. The emulsion drops splattered, broke into small droplets crackled, and when ammonium nitrate was present ignited d t h a loud pop.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1034
Emulsion fuels were also prepared containing various percentages of water and of 5 N ammonium nitrate solution as the internal phase. These fuels were run in a Cooperative Fuel Research (CFR) Diesel fuel testing unit, in accordance with ASTM specification ( I ) , and the cetane numbers were determined. Results are shown in Figure 2, each circle representing an average of four to seven runs, with a scatter of less than 1 0 . 5 cetane number. The emulsions used in the CFR Diesel engine tests were all of the water-in-oil type, as this involves little change in viscosity and maintains the lubricating qualities of the fuel. The emulsions were not buffered or inhibited, and are therefore particularly corrosive to stressed copper and brass components in the system. DISCUS SIOh-
From Figure 1it may be noted that the self-ignition temperature of the untreated Diesel fuel, as determined in the atmospheric pressure tester, is 418" F. Adding 4% water in emulsion form raises the self-ignition temperature 10" F., but adding 470 5 N aqueous ammonium nitrate solution t o the Diesel fuel lowers the self-ignition temperature 14' F.
Vol. 45, NO. 5,
Partly counteracting this ignition delay is another effect of the water. If u-ater which is not dissolved in the oil is present, each phase will exert its characteristic vapor pressure at a given temperature. At a particular pressure, the liquid water will immediately flash to a vapor, breaking up drops, when a high enough temperature is reached; above the critical temperature for water this vaporization will be independent of the prevailing pressure. This effect of blowing up of a fuel drop was observable with the emulsion fuels in the atmospheric pressure apparatus when ignition delay was studied. Surface tension and interfacial tension effects may account for the observed differences in wetting of the quartz plate, on which the drops were heated, by the Diesel fuel as compared to the emulsion fuels.
590 580 570
+
DIESEL FUEL
560 550 540 530 520 510
5
'
w
9 % a 2
E
500 490 480
470 460
0
450
2 4 6 8 IO 12 14 16 A D D I T I V E I N F U E L , PER CENT BY V O L U M E
Figure 2.
440 430 420 410 400 390 3 8 0 0 1 2 3 4 5 6 7 8 9 IGNITION DELAY
-
NO IGNITION
SECONDS
Figure 1. Effect of Temperature on Ignition Delay for Diesel Fuel with Emulsified Additives at Atmospheric Pressure Emulsifier E is Polyethylene glycol 400, di, tri ricinoleate
These results are what one might anticipate. Assuming that the heat transfer characteristics-specific heat, thermal conductivity, heat transfer coefficients-of the emulsified fuel drop and the plain Diesel fuel drop are of the same order of magnitude, ignition would proceed as follom: When the drop of the untreated Diesel fuel is heated on contact with the hot plate, a portion of the fuel vaporizes, the vapor thus formed is also heated, and when a high enough temperature is reached for a suitable air-fuel vapor ratio, rapid oxidation occurs and the drop ignites. Now if there is a little water dissolved in the fuel, this water will just increase the vapor pressure of the wet fuel a t a particular temperature, but no marked effects are likely to be produced. As water has a greater latent heat of vaporization than fuel oil, one effect of water would be to lengthen the time required to bring the oil vapor-air mixture to its ignition temperature.
I&
Effect of Emulsified Additives on Cetane Number of Diesel Fuel
When ammonium nitrate is present in the emulsified fuel, the drop behaves much like the water emulsion drop, as far as wetting plate surfaces or blowing up drops are concerned. However, any local heating of ammonium nitrate will result in its decomposition, at a temperature which is actually less than the selfignition temperature of the Diesel fuel. As this decomposition is exothermic, and independent of the air-fuel ratio, it could promote vaporization of a liquid fuel, and it could promote ignition if a suitable air-fuel vapor mixture be present. The data of Figure 1 show that ammonium nitrate definitely lowers the selfignition temperature and shortens the ignition delay time at a given temperature for Diesel fuel. Figure 2 shows that 5 N ammonium nitrate in aqueous emulsion form added to a Diesel fuel with an initial cetane number of 39 can increase the cetane number to 42. It is more significant to compare the performance of the ammonium nitrate additive with the performance of the mater additive alone. The ammonium nitrate actually raises the cetane number more than 10 points, because it must overcome the effects of the water. The cetane numbers obtained here were based on an injection rate of total fuel of 13 0 1 0.5 ml. per minute (1); thus when the total fuel has a considerable percentage of water, it may not be directly comparable with fuel which is 100% combustible. The data obtained in the atmospheric pressure apparatus (Figure 1)are in good qualitative agreement with results obtained on the CFR engine (Figure 2). Such agreement between these tests has been observed previously ( 8 ) . Though limited to ignition delay a t atmospheric pressure and a t the pressures of a compression ignition engine, the data herein
May 1953
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
reported indicate wide possibilities for further research. More concentrated solutions of ammonium nitrate can be emulsified, since ammonium nitrate is highly soluble in water. I n localities where oil is expensive or unobtainable but where hydroelectric power is cheap and nitrogen fixation facilities are in use, there is the possibility of considering charcoal, or powdered coal, suspended in ammonium nitrate solutions as a liquid fuel for use in Furnaces or combustion engines. A possible application of emulsified fuel is its use in a gas turbine. Normally a significant fraction of the power developed by a gas turbine must be expended in the compressor to deliver large quantities of excess air, required by the gas turbine to maintain temperatures low enough for the turbine blades to withstand. This cooling effect could be accomplished by water as well as by air, and i t would take less energy to pump liquid water than to pump sufficient air for equivalent cooling. Actually, water injection has been used in the gas turbine (IO),but the use of water as a coolant by using aqueous emulsion fuels has not been reported. Problems arise in maintaining smooth combustion, due to slug flow and lubrication difficultics if appreciable quantities of water are present in a fuel. However, it is believed that maintaining the water in emulsion form will eliminate such problems, and the use of ammonium nitrate additive will assure smooth combustion. A large quantity of water is required for use of emulsified fuels under these conditions, and this would be considered as a disadvantage for aircraft or for automotive applications. However, this apparent disadvantage is not present in stationary power plant applications, or for power plants for vessels or railroad propulsion. Therefore, the use of aqueous emulsified fuels for gas turbines should be seriously considered and warrants further investigation.
1035
ACKNOWLEDGMENT
The authors wish to express gratitude to C. J. Vogt for helpful criticism, valuable advice, and sustained interest in this investigation. LITERATURE CITED
American Society for Testing Materials, Philadelphia, “8.8. T.M. Standards on Petroleum Products and Lubricants,” D 6 1 3 4 1 T , pp. 190-7, 1942.
Babor, J. A,, “Basic College Chemistry,” pp. 332-3, New York, Thomas Y. Crowell Co., 1946. Belknap, C. B., U. S. Patent 1,533,158 (April 14, 1925). Bichowsky, F. R., and Rossini, F. D., “Thermochemistry of the Chemical Substances,” p. 34, New York, Reinhold Publishing Corp., 1936. Boodberg, A., and Cornet, I., IND.ENG. CHEM.,43, 2814-18 (1951).
Ellis, Carleton, and Meigs, J. V., “Gasoline and Other Motor Fuels,” p. 11, New York, D. Van Nostrand Co., 1921. Hodgman, C. D., editor, “Handbook of Chemistry and Physics,” 31st ed., pp. 401, 1497, Cleveland, Chemical Rubber Publishing Co., 1949. Hunter, E., Proc. Roll. SOC.(London), Series A, 144, 386-412 (1934).
Lewis, G. N., and Randall, Merle, “Thermodynamics and the Free Energy of Chemical Substances, p. 606, New York, McGraw-Hill Book Co., 1923. Norman, C. A,, and Zimmerman, R. H., “Introduction to GasTurbine and Jet-Propulsion Design,” pp. 57-63, New York, Harper and Brothers, 1948. Pease, R. N., “Equilibrium and Kinetics of Gas Reactions,” pp. 129-34, Princeton, Princeton University Press, 1942. Shah, M. S., and Oza, T. M., J . Chem. SOC..(London), 1932, 725-36. RECEIVED for review April 14, 1952. ACCEPTED December 20, 1952. Presented before the Division of Gas and Fuel Chemistry at the 122nd MeetCHEMICAL SOCIETY, Atlantic City, h’. J. ing of the AMERICAN
Physical Properties of Oil-Enriched Rubbers I
