MAY, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
million cubic feet of gas when the solution, regenerated a t 90" C., enters the scrubber at 35". This estimate is based on a concentrated solution containing 22.5 moles of ammonia per 100 moles of water. The possible loss in this manner is less when the dilute solutions are considered. A comparison of the solubility data of sulfur dioxide in these ammonia solutions a t low partial pressures with those in n-ater (5) indicates that the available solubility in the ammonia solutions is approximately 160 times that in mater.
Literature Cited (1) Bichowsky a n d S t o r c h , J . Am. Chem. Soc., 37, 2696 (1915) (2) Goodwin, "Precision of M e a s u r e m e n t s a n d G r a p h i c 51 Methods," New Y o r k , McGraw-Hill Book Co., 1913.
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(3) I s h i k a w a a n d H a g i s a w a , BUZZ. Inst. Phys. Chem. Research ( T o k y o ) , 10, 166 (1931). (4) J o h n s t o n e a n d Keyes, IXD. ESG.CHEY.,27, t o be published (1935). (5) J o h n s t o n e a n d L e p p l a , J . Am. Chem. SOC.,26, 2233 (1934). (6) Jones, Carnegie I n s t . W a s h . , Pub. 170, 140 (1912). (7) Kraus, " P r o p e r t i e s of Electrical C o n d u c t i n g Systems," p. 149, New York, Chemical C a t a l o g Co., 1922. ( 8 ) R a m s e y , British P a t e n t 1427 (1553). (9) R o t h a n d Zeumer, Z. Elektrochem., 38, 165 (1932). (10) Speller, " C o r r o i o n Causes a n d P r e v e n t i o n , " p. 2 6 , S e w Tork, X c G r a w - H i l l B o o k Co., 1926. (11) T e r r e s a n d H a h n , Gas- u. TT'asserfach, 70, 339, 393 111927).
RECEIVED February 4 , 1935. This paper contains part of the results of a cooperative research Project No. 34, with the Utilities Research Commiesion, Inc., entitled "A Study of Stack Gases." I t is published by permission of the Director, University of Illinois Engineering Experiment Station.
Antiknock Effect of Tetraethvllead J
Effectiveness of Tetraethyllead in Increasing the Critical
Compression Ratio of Individual Hydrocarbons JOHN RI. CAMPBELL, FRANK K. SIGNAIGO,' WHEELER G. LOVELL, AND T. A. BOYD Research Division, General Motors Corporation, Detroit, Mich.
REVIOUS publications
Quantitative measurements of the speeffect of tetraethyllead in sixty-two individual hydrocarbons were made by finding the increase in critical compression ratio, in a single-cylinder variable-compression engine, made possible by the addition of tetraethyUead in a concentration Of la0cc* per gallon* Upon this basis there are as many as variations in the effectiveness of tetraethyllead in suppressing knock in different hydrocarbons. certain general relationships between hydrocarbon structure and suscePtibilitY to lead which to be consistent within the scope of this work are described.
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laboratory (8-12) have presented data on the knocking behavior of a large number of hydrocarbons as measured both in dilute solutions and also as measured by the critical compression ratios of the compounds themselves. Such data show that hydrocarbons exhibit a range of knocking behavior which is very large as compared with present commercia1 fuels. The widespread use of tetraethyllead a s a n a n t i knock agent to increase the compression ratio a t which a fuel may be used w i t h o u t k n o c k has caused some attention to be given to its effectiveness in increasing antiknock value of different individual hydrocarbon fuels. The data of this paper show that lead has a range of effectiveness in different pure hydrocarbons which is very large as compareri with its effect in present commercial fuels. However, the present data relate to pure hydrocarbons, and the behavior of mixtures cannot necessarily be inferred from the behavior of the constituents in regard to their susceptibility to tetraethyllead. i lnumber of investigators have reported data on the effectiveness of lead in hydrocarbon mixtures. I n 1932 Garner, Wllkinson, and Kash (5) found that the effectiveness of tetraethyllead a t a Concentration of 1 CC. Per gallon (3.79 liters) in increasing the octane number Of 20 per cent solutions of five alpha-olefins in a base fuel increased with the molecular lveight from pentene through nonene. Similar data were also obtained by Garner and Evans (4) on twenty-one 1
Present address, Unir ereity of T'isconsin, Madison, Wis
h y d r o c a r b o n s , including ammatics, cyclohexanes, and cyclopentanes, also in 20 per cent solutions; and they concluded that the order of increasing effectiveness w a s a r o m a t i c s , cyclohexanes, cyclopentanes, as measured in these s o l u t i o n s . Hebl and Rendel (6) in 1932 showed that the effectilreness of tetraethyllead in increasing the a n t i k n o c k v a l u e of gasolines varied with the fuel used. Alden in 1932 ( I ) and also Hebl, Rendel, and Garton (7) in 1933 presented data on the effectiveness of lead in a variety of gasolines. It may be expected that data o n t h e e f f e c t i v e n e s s of lead in known hydrocarbon mixtures and more especially in individual hydrocarbons would be of interest a t this time. It is the purpose of this paper to present data which have been accumulated over a period of years on the effectiveness of lead in increasing the critical compression ratio of sixty-two individual hydrocarbons.
Method of Measurement Measurements of the effectiveness of lead in these compounds were made in terms of the difference in the critical compression ratio of the hydrocarbon with and without the addition of tetraethyllead in amounts corresponding to 1 cc. per gallon of fuel. I n some cases where the effect was small, g e a t e r amounts of lead mere added, and the effect per cubic centimeter was computed, assuming a linear relationship between effect and concentration over this range, since the deviations from linearity of the relationship are believed to introduce a negligible error in such cases.
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IhDUSTRIAL AND ENGINEERING CHEiMISTRY
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compound, only a few minutes apart, the order of accuracy or reproducibility obtained for these differences is of a much higher order than might otherwise be expected. The rate of change of knock intensity with compression ratio as determined by ear has not appeared to vary greatly with changes in compression ratio; in other Qords, the intensity of knock produced b y a given increase of compression ratio does not appear to vary within the range of compression ratios between 3 to 1 and 15 to 1.
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2 INCREASE IN C O M P R E S S I O N RATIO ' FCR I CC. TETRAETHYL LEAD PER GALLON l
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FIGURE1. EFFECTIVENESS OF T E T R A E T H Y L L E 4 D SION R A T I O S OF
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HYDROCARBONS
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NUMBER OF CARBON ATOMS I N MOLECULE
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CONPOUNDS ON EFFECTIVENESS OF TETRAETHYLLEAD
This critical compression ratio TT as deterniined in a singlecylinder t-ariable-compression engine previously described ( 3 ) and is defined as that a t which knock becomes just audible in a quiet room under the following conditions of operation full load, engine speed 600 r. p. m., jacket water boiling, mixture ratio and spark timing for maximum power. Thiq procedure is somewhat similar to that used by Ricardo (18, 14) for determining the "highest useful compression ratio" (H. U. C. R.), except that the engine speed is different. Since the absolute effectiveness of lead as measured in thii way would be expected to be influenced by engine condition< (4), the data reported here pertain only to the particular engine and conditions used. These conditions correspond approximately to those used in the C. F. R. Research method of knock rating, and some deviations may be anticipated for other engine conditions. The absolute values of the critical compression ratios used in these determinations were found to be usually reproducible within *0.1 of a ratio a t comprewion ratios between 3 and 5 and within *0.5 between 12 and 15. However, since the values for the effectiveness of lead were obtained from successive deterniinations on the fuel with arid without the lead
Most of the hydrocarbons investigated in this work were synthesized in these laboratoriec. The following compounds, obtainable commercially, mere redistilled just prior to use in the engine: n-pentane, 2-methylbutane, nhexane, n-heptane, 2,2,4-trimethylpentane, 2,7dimethgloctane, cyclohexane, cyclohexene, decahydronaphthalene, indene, dlcyclopentadiene, CO\lPRESd-linionene, dipentene. The olefins 2,2,4-trimethyl-3-pentene and 2,2,4-trimethjM-pentene were supplied by F. C. Whitmore of Pennsylvania State College. The compounds represent t h e same samples as those on which data were previously reported (12) in the investigation of the critical compression ratio of the hydrocarbons themselves. Many of these hydrocarbons were made b y the alcohololefin-paraffin method which has been described in previous publications from this laboratory (11, 16) for the preparation of alicyclic and aromatic hydrocarbons. I n this method an alcohol, usually prepared by the Grignard reaction, is dehydrated by distillation from a suitable catalyst to an olefin which can then be catalytically hydrogenated to the paraffin. This hydrogenation was accomplished by shaking a glacial acetic acid solution of the olefin with a platinum oxide catalyst under a pressure of 2 to 3 atmospheres of hydrogen. Table I lists the alcohols so dehydrated, the first two columns giving the starting materials used for the G r i g n a r d s y n t h e s i s or other source of the alcohol. The f o u r t h c o l u m n lists the dehy0.6 dration catalyst used, the fifth column lists the resulting olefins, m= mnf and the last c o l u m n gives the corresponding paraffin prepared 11y hydrogenation of the olefin. The follom ing olefins were prepared by adding allyl b r o m i d e
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1-pentenefrom ethyl bromide, l,5hexadiene from allyl bromide, 1p~~~~~~ o ~ $ ~ ~ A Iieptene ~ from n-butyl bromide, 2-methyl-5-hexene from isobutyl 3. EFFECT OF bromicie, 3-methyl-5-hexene from POSITIOX OF U X E A T U R 4 E ~ ~ ~ ~sec-butyl ~ ~ ,bromide, . ~ - and 1-octene TION ON SESS OF TETR.4ETHYLfrom %-amyl bromide. LEAD The a c e t y l e n e hydrocarbons were prepared according to the methods of Bourguel (NO) as follows:
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3-HEPTESE. Dipropylcarbinol (Table I) n-as oxidized t o dipropyl ketone which mas treated with phosphorus pentachloride to give a mixture of 4,4-dichloroheptane and 4-chloro-3heptene. This mixture xyas then treated with qodium amide to give the acetylene compound.
t MAY, 1935
INDUSTRL4L AND ENGINEERIXG CHEMISTRY TABLEI.
Carbonyl Compound >.lkyl Halide (Commercia',) Boetone Etihyl bromide (Reduction of acetone with 519) n-Butyraldehyde n-.Propyl bromide Diethyl ketone Eithyl bromide Acetone Iaohutylbromide (Cyclopentanone f r o m adipic arid) Crotonaldehyde Ethyl bromide Diethyl oxalate E t h y l bromide
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_ _ _ _ _ - ~ - PREPAR.4TIOS O F
HYDROCARBOXS BY
Alcohol Diethylcarbinol Dimet hylethylcarbinol 2,3-Dimethyl-2,3-butanediol Di-n-propylcarbinol Triethylcarhinol Dimethylisobutylcarbinol
Cyclopentanol A-2-Hexenol-4 3,4-Diethyl-3,4-hexanedio 1
~-HEPTYNE. Heptaldehyde was treated with phosphorus pentachloride to give 1,l-dichloroheptane and 1-chloroheptene. This mixture on ~eactionwith sodium amide gave the acetylene compound. 2-OCTYNE. Tk.e sodium amide complex of 1-lieptyne n-as methylated with dimethyl sulfate to give the acetylene compound. CYCLOHEXYL.~CICTYLENE. Cyclohexylmethylcarbinol was prepared from acetaldehyde and cyclohexyl magnesium bromide. This was oxidized t o cyclohexyl methyl ketone which was treated with phosphorus pentachloride to give the corresponding halogen compound
