Octane Ra ings of Agricultural WIotor Fuels C. F. ELDER, F. R . TRUBY. .\orthern
€
4 \ RICH,IRD ~
WIEBE
Regional Research Laborator?, L . S . Departriierct of I g r i c u l t u r e , Peoria, I l l .
S CO~~SEC'TIO R.ith l ~ work on the behai+ior of ethanol and
IVitle di.c.ix,lxiiic'ie>in the octane rating of mc.thanol and clthanol, in tlie paat: r i m he espl,iinc,tl for the which ha\.(, I ~ ~ ic.ported cn moat part as heiiig due to these difficulties: lion. attention to all t1ct:tils does not result in agreement twtn-cen operators nittiin the supposed limits of accuracy. 7;-2 oct:ine numbers of et11:tnol reported in tlic. literatiire vary froni !IO to $19, and a few of the data are summarized as follon.-:
other possihle fermentation products in internal combustion engines, octane ratings of a large number of blends (mostly anhydrous fuels) were determined. Four methods are available for rating fuels: C.F.R. Research or F-1 method, LIotor or F-2 method (d.S.T.RI. 357-44), F-3 test, for aviation fuels (A.S.T.M. 614-44T), and the C.F.R.supercharge or F-4 method. With a few exceptions the d a t a reported in this paper Ivere obtained with the F-2 method, since i t is still the standard laboratory procedure for rating automotive fuels; only brief reference is made to F-1 and F-3 results obtained at this laboratory and elsewhere. Unsaturated types of gasolines may have F-1 ratings considerably higher than the corresponding F-2 values (sensitive fuels), and for such fuels the F-2 method may not be as good a n indicator of their behavior on the road; actually i t may be misleading ( 1 , 9). For sensitive fuels the F-1 method appears to be a better indicator of road performance than the standard F-2 procedure. Ethanol belongs to the class of sensitive fuels; hence the F-2 results are not the sole criterion for judging its behavior as a fuel. I n general the F-1 ratings of ethanol and its blends, which have F-2 octane numbers in the neighborhood of 90, are above 100, and thc F-1 rating of ethanol itself, according to Puekett ( 8 ) ,is equal to iso-octane plus 1.4 ml. tetraethyllead (T.E.L.). Thus far no satisfactory way of extending the octane scale above 100 has been evolved, which makes correlation difficult. This difficulty mag be overcome, however, if a leaded triptane-heptane scale is adopted, as recently proposed by Brooks (3).
Bridgeman ( 2 : H e r o n xiid Reittty ( 6 ) Eglof? and \-an hrsdell ( 5 )
-l ' l l p k o t f
1 j l8,)
Value given in this article
The valuc: ( i f 99.7 is 0.7 unit higher than tlie one prc3vioiisly reported ( 7 ) and rcprewnts the average of tn-o sets of values obtained independently by t w o of the authors. Brooks and Cleaton ( 4 ) report that the standard d tion of F-2 cwlia~i:c group samples during 1939-41 \vas 0.48 unit and that the gre:ite>t m t z i muin and niininiuni deviations were 2.0 and 2.2 u n i t , rcspectively. Discrepancies among individud ratings quickly tii;appear as lon-er alcohol concentrations are appri)achctl, and a ~ i c e mentis then obtained within the limits of accuracy of the method. Tables I arid I1 give results of ethanol blends ivith paraffin>, iso-octene, aromatics, and cyclohexane. Some of the data from these tables are plotted in Figures 1 and 2 . Ainilincis the most effective compound for raising the octane nuniber of ethanol. The effectiveneis of higher aromatic amines, such as toluidine m i l xylidine, is much lower; and lengthening of the side chain, as in n-butyl aniline, actually lon-ers the octane number of ethanol. Addition of 2 5 5 of isoparaffins, such as neohexanc or S-3 refcxrence fuel, causes a greater increase in octane number than a similar addition of benzene, although the octane number of bvn-
THE F-2 method v a s designed to rate petroleum fuels, and trouble is encountered in testing fuels, such as ethanol, having a high heat of vaporization and requiring different fuel-air ratios.
r 85
i
80
0
25 50 75 VOLUME OF BLENDING AGENT AT 60"E, PERCENT
750 100
IO0
VOLUME 25 OF BLENDING AGENT 50 AT 60'B,PERCENT 75
Figure 2
Figure 1
508
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1947
TABLE I. F-2 OCTANE NUIIBERS OF E r H a u o L BLESDEDWITH ISO-OCTESE, NEOHEXAKE, AND VARIOU:, REFERENCE FUELS 50 85.0 84 8 84.7
T'olume 75 82.5 84.4 84.2
94.2 91.4 92 4 90.5 92.6
95 6 99 0 +0.2ml.a 99 o 98 6 99 0
7
Fuel
25 88 0
I3o-octene Iso-octene 1 ml. T.E.L./gal. Iso-octene 2 ml. T.E.L.iga1. Iso-octene 3 ml. T.E.L./gal. Seohexane 1 mi. T.E.L./gal. Neohexane Seohexane 2 ml. T . E . L . / g a l . S-3 reference fuel 5-3 t 1 nil. T E.L./ga! 5-3 T 2 nil. T.E T,./gai.
92 2 88 3 69 1 94.0 89 7 89 5
90 octane S o reference luel 90 octane S o . 1 1111. T . E . L . / g a l . 7 0 . 2 octane S o . reference fuel 60.0 octane S o . 60.0 octane Xo, y 1 nil. T.C L ' g a l . 60.0 octane S o . L 4 nil. T.E.L.'gal.
90 7 88 6 89 1 88 7 88 1 85.5
++
85 4
85 0
+ ++
..
..
% Fuel i n E t h a n o l
..
02 4
85
90
.. .. , . ..
..
95
..
,
.
.. .. ..
.. .. , ,
,.
.. .. , .
.. , . ..
100 79.8 814 83.2 84.0 95.1
.. .. .. .. ..
..
, .
..
..
997 1, l l l ~ . +2.OSnil."
+ n
., ..
~
509
only on a series of three-dj iiieniioiial oblique plots, a satisfmtory comparison cannot be made. In general agreenicnt, XTitli data presented in this article, \\-idmaier finds that :ilcoliol coiictsntrations of 20 to 4 0 5 alcohol with win11 amounts of l c d are most effectivc:.
ThBLES 11- and V give octane nmnhers of various vtbanol and acetoric blend?. The valws in Darentlimes are those ohtaincd by 1'uel;ctt (81and arc> ~~
+
u
8i.i
86.7 86 6
85.8
91 2 9 6 0 9712 (6 6 ..
9;:s
..
.
86'
85
A HO\lhTICS
F u e l i n Ethanol, Vol. 70 5 Aniline 93 3 Aniline 1 mi. T E L. 88 5 . 4 n i l i n e + 3 m l . T . E . L . 8i.4 Toluidine 91.3 Xylidine 91.0 Benzene Isopropyl benzene Cyclohexane Toluene n-Butyl aniline 8i.9
BLEZDED inm
ErH.IsOL
.4KD C T C L O H E X I S E
10 20 96 n +o.o4 1111." 90.6 . 91 3 9 2 . 1 9i.n 9 2 . 1 92 3 90 0
91.4 84.6
..
..
..
25
50
75
9i:o
91'9
9i:i
:1
8S:2 92 2
85:2 92.5
82'3 96 0
78'4
..
..
100
..
,.
..
Equivalent to iso-octane plu; indicated amount of tetraethyllead.
90
in good agrwniont xi:h o ~ i row^, Sni:ill aiiiounts of nxtcr 1i:ivc a d~~c.itiet1 in84'1 80.3 fiuciicc and, unless prc'cautiorl>are tnlien, may w G i l y account for a 1iighc.r octane rating of etlianol. .As shown in Talde 1-1,lair- concentration. of esters arc anprosimately neutral. Pro-linock conipounds, such as fert-but yl tiydroperoside and isoamyl nitrite, used as ignition accelerations, l o w r the rating of ethunol nilich lezs than that of a 90 octane number reference gasoline (Table VI1 and Figure 4). I n the cascx of leaded ethanol plus 2 nil. of tetrac,thylie:id. tert-butyl hydroperoxide either counteracrid the cffwt of the tc~traethylleadpresent or destroyed it entirely. hlcoliols like benzene and otlier aromatics are fuels \v-liich vary greatly in antilcnncli quality under lean mixture and rich niisture i0:2 600
..
76.6
Equivalent to iqo-octane pluq indicated amount ol tetraethyllead,
TABLE 11. F-2 OCTANENUMBERS OF
a
91.2 '31 6 83 2 79 0 83 2 86 2
91 88 9
70 2
00,
z c i i ( ~is 100+ (extrapolated value), whereas. those of the former are !)>.I and 99.7. res:pcctivc,lv.
Tetraethyllead depresses the octane nuinbcr of pure ethanol as iwll as that of soiiicx higher :tlocliols (Table 1111, and it is iniportant to know to x1i:xt extent silch a dctrinic~iit.ileffect per95 , It appcars tiiat tiit. action of inoderate amounts etlianol is iiidc,pendcnt in blends cont:iining up to a about 2 5 7 of ethanol; for higher ethanol conten; the difference m is relatively sniall unless the gasolinc is highly leaikti. F i g r e 3 3 shows that identical values are obtained for t v o gasolines of Y octane number 70.2 blendcd with 2 5 5 of ethanol: one is clcar f 90 and the other contains 1 nil. of tetraethyllead per gallon. Hon-- V N ever, the presence of 4 nil. of tetraethyllead per gallon definitely L lon.ers the rating of blends which contain mnre than 2OCc ethanol. 1 I c t I i a d has zero lead susceptibility, whereas teri-butanol sho\Yj a high blending lead susceptibility. E5 IYidmaier (11).investigated estensively the lead susceptibility of various alcohols and isopropyl ether blended with two gasolinei: (octane nunibcr; of 11.7 and 63.5). Since his data are sh0n.n
1
01 ETHYL
I1
b
TABLE 111.
Methanol Ethanol Isopropanol n-Butanol 50-50 n - b u t a n o l 4 0 0.X. ref. fuela Isopentanol 50-50 isopropanol-80 O . S . ref. fuel 50-50 tert-butanol-80 O . S . ref. fuel 50-50 tert-butanol-90 O . K , ref. fuel Iso-octene 60 O . N . ref. fuel Reference fuel 50-50 ethanol-80 0 . S . ref. fuel 20-30-50 ethanol-methanol-80 O.X ref. fuel
0
0.15 87:3
..
85:4
..
6 93 4 77 5 60
90 85 92 81 85 84 89 96
+o
0 0 8
5 7 0 7 201111.5
:
90 86 6
98 0 85 1
89.1
88 9
O . S , ref. fuel = octane number reference fuel Equivalent t o iso-octane plus indicated amount of tetraethyllead.
I
Iv
N-BUTANoL'
Figure 3
1.0
0.60
I
25 50 VOLUME OF BLENDING AGENT AT 60'E, PERCENT
TETRaETHYLLEAD SCSCEPTIBILITY OF VARIOUS ALCOHOLS,
T.E.L. Added. hfl./Gal.
a b
ETHEA
REFERENCE FUELS, .4KD RI.ESDS 2.0 90.0 85.0 92.8 81 5 86 5 84.2 90 99 83 2
-0 09 nil b 86 0 89 0
3 0 90.0 85.0 92.8 81.8 87.0
4.0 90.0
90:7 +O 18ml.b 8410 80.3 86:s 88.9
Si16 89.1
I oc
510
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE IT. F-2 OCTASEN U M H E R S Fuel i n E t h a n o l , \'ol.
5
5
..
+
Fuel i n Acetone, 1-01
CC
..
Ethanol Ethanol 1 ml. T E L / gal. Butanol 90 octane S o . reference fuel 90 octane S o . reference 1 mi. T.E.L.: fuel gal. 90 octane S o . reference fuel 2 ml. T.E.L., gal. 70.2 octane S o . reference fuel 50 octane S o . T 1 nil. T . E . L /gal
. . . .
93,6(93.X)
..
96.'.
y9:3
10
.. ..
..
..
..
..
98.6
99.0
..
,
.
..
..
50
.. ..
95:3
99:a
94:a
99:o
'31 1
98.2
..
88.8 99 3
.,
91 3
99.0
..
..
..
7.5 93.5
50
.
f 0 . 2 4 nd
.. ..
..
'3i:s 92'4
99.8
.
80 ,
.
'30 01.8
. .
.
.
100
.,
90
.
.
96.4
86.7
..
99.5
Y 3 . 5 91 1 9 0 . 8 '30.4
.
.
. . . .
..
'I
. . . . . .
. .
..
96.5
8 5 . 0 Ti,;
