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Sept. 17, 1946.-
-R. F. MARscHNER
Y
2,407,716
SUPER FUEL
`Filed June 29, 1940
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Sept. 17, 1946.
R. F. MARSCHNER
2,407,716
SUPER FUEL
Filed June 29, 1940
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Patented Sept. 17, 1946
2,407,216
UNITED STATES PATENT OFFICE
2,407,716
SUPERFUEL
Robert F. Marschner, Chicago, Ill., assignor to
Standard Oil Company, Chicago, Ill., a corpo
ration of Indiana
Application June 29, 1940, Serial No. 343,179
4 Claims.
l
(Cl. 44-69)
2
This invention relates to a new and improved
super fuel particularly for aviation purposes and
thenes, it has a higher heat Value than aromatics
(due to its higher hydrogen-to-carbon ratio) and
it pertains more particularly to improved meth
cds and means for obtaining cyclopentane and
cyclopentane-neohexane blends. The invention
also relates to motor fuels comprising isooctane
cyclopentane and isooctane-cyclopentane-neo
hexane blends either with or without the addi
tion of tetra alkyl lead.
An object of my invention is to provide an avi
ation fuel superior to any heretofore known >and
particularly with respect to octane number and
ritical compression ratio, coupled with an opti
mum volatility range and response to tetra alkyl
lead.
Cyclopentane is superior in its blending octane
value to any other hydrocarbon fraction of motor
fuel. Thus the blending value of cyclopentane
may range from about 115 to 160 octane num
bers by the research method depending upon the "
fuel into which it is blended and the concentra
tion. The rating of aviation fuels should be
under the supercharged conditions of actual
flight. Since the C. F. R.-R. method is a fair
it is more stable and more responsive to lead tetra
UI
ethyl than oleñn hydrocarbons. This c-ombina
tion of the desirable properties of extremely high
octane number, volatility of the proper magni
tude and extreme chemical stability, together
with sensitivity and heating value, make cyclo
pentane of unique value as an aviation fuel con
stituent. An object of my invention is to utilize
the high blending octane number, the stability,
the sensitivity and the volatility qualities of cy
clopentane together with commercial isooctane
to make a motor fuel having an octane number
about 100 or higher even in the absence of tetra
alkyl lead and having much greater octane num
bers when small amounts of tetra alkyl lead are
employed.
Cyclopentane as heretofore recovered by the
close fractionation of naphthas has not been en
tirely free from normal pentane and has con:-
tained relatively large amounts of methylpen
tanes. For example, an A. S. T. M_ 5% to 95%
range of 104 to 140° F. may usually indicate the
indication of supercharged performance, “re
presence of as much as 20% n-pentane and 40%
search” octane numbers are more significant in
Z-methylpentane.
connection with aviation fuels than are the “mo
tor” octane numbers. The C. F. R.-~R. octane
cure such a bo-iling range from a mixture of n
number of cyclopentane is above 100.
-
It is entirely possible to se
pentane and 2-methylpentane, only, without any
cyclopentane whatsoever. Furthermore, there
Cyclopentane is inert to cold concentrated sul 30 has been no appreciation of the fact that neo
furie acid,` does not respond to the usual tests for
hexane boils Within 1° F. of the cyclopentane so
unsaturaticn, is stable to atmospheric oxidation
that when the narrow boiling range of the frac
and produces no gum on standing in contact with
tion is the sole criterion, a product which is as
various metals. In short, it exhibits all the sta
bility characteristics demanded by aviation gas
olines. Cyclopentane has a boiling point of 121°
sumed to be cyclopentane may, in fact, be chief
1y neohexane. I have discovered that a cyclo
pentane-neohexane composition which is sub
stantially free from normal pentane and meth
F. and a Reid vapor pressure of about 10 pounds.
These properties are highly desirable in an avia
ylpentanes is' a remarkably superior blending
tion fuel for starting and acceleration purposes.
agent for isooctane aviation fuels, particularly
Cyclopentane has an additional advantage of a 40 when the proportion of cyclopentane to neohex
high sensitivity, a property which is rare among
ane ranges from about 1:3 to 9:1. This mix
chemically inert and stable hydrocarbons. Sen
ture of from about 30% to 90% of cyclopentane
sitive hydrocarbons have the general property of
With about 70% to 10% of heohexane is so dis
permitting high engine power outputs when a
tinctly new as a commercial product and it offers
deficiency of air with respect to fuel is supplied
such remarkable advantages in an isooctane av
to the engine, i. e., under “rich mixture” condi
iation super fuel that I have given it the name
tions. A highly sensitive hydrocarbon fuel is par
“ultrane” Ultrane has a Reid vapor pressure of
ticularly advantageous for military aviation pur
poses for “taking off,” climbing, etc. Cyclopen
'tane‘is the most sensitive o_f all tested naph-r
about 8 to 10 pounds. It boils within the nar
row limits of 120 to 124° F. It has a refractive
index above 1.38, an A. P. I. gravity be1ow'75", an
4
3
Russian and South American light naphthas con
tain similar amounts of ultrane.
In practicing my invention I fractionate light
virgin naphthas from any crude, or any other
wise derived light naphthas which contain appre
ciable amounts of ultrane, under carefully con
trolled conditions to obtain a hydrocarbon frac
the range of about 200 to 240° F. and it has a
tion boiling from about 80 to 150 or 160° F. and
Reid vapor pressure of only about 2 pounds. By
preferably boiling within the range of 100 to 140°
blending about 30 to 70% of ultrane with 30 to
70% isooctane, preferably equal parts of ultrane 10 F. as determined by ordinary distillation. This
fraction which mayV be termed “ultrane concen
and isooctane, the resulting motor fuel has an
trate”> will be contaminated >with normal. pentane
ideal volatility *for-Y aviation purposes, itis re
and even with normal hexane, both of which have
markably-stable against gum formation and de
extremely low octane numbers. It is essential,
terioration of all kinds, it offers exceptionally '
therefore, to separate the `ultrane fraction from
valuable starting and acceleration characteris
Vthese contaminants. Study of the boiling points
tics and it is characterized by a clear octane
' of hydrocarbons shows that within the boiling
number of at least about 100 C. F. R.-R.
range of about 100 to 160° F. the only hydrocar
It has been proposed to substitute a dilute
octane number above 95 C. F. R.-R. and a blending octane number which may be as high as 160
C. F. R.-R.
Commercial isooctane may have an initial boil
ing point of about 165° F. but between the 10°
and 90° points the boiling temperature is within
cyclopentane fraction for- the normal pentane
content of an ordinary gasoline and even of avia
bons present are:
,
tion gasoline but my invention distinguishes from
such proposals in several respects. In the first
place, my ultrane has a boiling range of only 4
or 5 degrees F. and althoughk a slightly wider
n-Pentane _________________ ._
lboiling range may be permissible, it is essential 25
Neohexane ________ _ _
' that the ultrane should be substantially free from
normal pentane. In the next place, ultrane is
prepared from such charging stocks that it has
Y
y
20
.
Boiling
Hydrocalbo“
A; P. I.
point,°F.
Oyclopentane. _ _ _
96. 8
_
C. F. R.-R.
gravity
octane No.
94. 5
120. 5
A58. 2
121. 5
85. 0
80. 9
61
Above 100
’
92
2,3-dimcthylbutane... _
__
136. 2
Z-methylpentane _ _
_.
140. 4
83. 4
73
B-methylpentane _ _
n-hexane _______ __
_
145. 6
155, 8
79. 9
81. 4
Above 100
75
25
a certain proportion of cyclopentane to neohex-vv
ane, the cyclopentane preferably predominating
to the extent of about 2:1 and the over-all limits
being about 30 to 90% cyclopentane and 70 to
10% neohexane. Finally, the lultrane is not
Traces of
boiling as
from the
neohexane
benzene will be `found in fractions
low as 140° F. It Will be notedA
above table that cyclopentane and
boil within 1° of each other and
-blended with ordinary gasolines such as are pro
commercial separation of these two by frac
duced by thermal or catalytic cracking or reform 35 tionation -is practically impossible. In prac
ing or such as are produced by hydrogenation of
ticing my invention I effect close fractionation of
>oils or the polymerization of refinery gases. The
my ultrane concentrate in order to remove there
,isooctane with which my ultrane is blended is a
from the n-pentane, which is characterized by
synthetic hydrocarbon which may be obtained
a high A. P. I. gravity and a very low octane .
`'byithe alkylation- of clef-ins by means of‘iso 40 number, together with substantially all the nor
vparaiïins to produce isoheptane, isooctane, iso
mal hexane which is characterized by a relatively
nonane or isodecane, or it maybe produced by
high gravity and an even lower octane number.
the selective polymerization of oleiins (such as
`The ' 23.7° boiling point differential between
butylenes or pentenes to produce isooctene or
n-pentane and cyclopentane makes commercial '
’isononene or isodecene) followed by hydrogena 45 fractionation between these two hydrocarbons
‘tionof isooctene to isooctane, isononene to iso
‘ commercially feasible. It is a little more diñicult
`nonane or isodecene to isodecane. The isooctaneA
to obtain a sharp fractionation commercially be
to which this invention relates is the commercial
tween neohexane and 2,3-dimethyl butane be
rather than chemically pure product but it is
cause in this case the boiling pointV differential is
characterized by the absence of appreciable 50 only 14.7°. However, sharp fractionation at this
'amounts of' low boiling hydrocarbons, its 10%
-point being about 200° F, and its 90% point being
point is not as important as in the lower range
since the 2,3-climet/hylV butane is more valuable
about 240 to 270° F. When such isooctane is
than the neohexane as a blending agent. It is
blended with about 30 to 70 parts by volume of
only necessary to prevent any substantial amount
ultrane, the resulting motor fuel is superior in 55 -of the methylpentanes or n-hexane from contam
performance to any motor fuel which has here
inating the ultrane and this I have found can be
tofore been known.
easily done in .commercial operations. 1 prefer
From extended laboratory research and the
to retain as little as conveniently possible of the
study of all available literature, I have found that
2,3-dimethyl butane in the‘ultrane since contam
ultrane is present in almost all light naphthas 60 mation with much >2,3-dimethy1 butane also in
'from all types of crude petroleum. The amount
cludes. some methylpentanes.
*of ultrane in various light naphthas containing
_the C5,` Cs and Cv hydrocarbons in the crude are
as follows:
`
Ultrane
Crude source
content
`
My
invention
also
_
Per cent
Pennsylvania__ __- ____________________________________ _ _
West'Virginia.
_ _ _ _ _ _ _
_ _ _ _ _ _ _ _.
___
2-3
Texas ..... __
2-4
Michigan
3-4
Oklahoma
4-8
Califolnla
Wyom1ng___
5“ 7
__
Louisiana _____________________________________________ _.
5-7
5-10
improved
ponents of light naphthas and means for frac
65 tionating -the ultrane itself into its> component
parts, the .latter being-.preferably accomplished
Y ,by means of azeotropic distillation of the ultrane
with methanol.
'
contemplates
means for fractionating ultrane from other com
The inventionr will be more
clearly' understood from the following detailed
70 description and from vthe accompanying drawings
which form a part `of this specification and in
which
l
_
Y
.
1
,
_Figure 1 is a vdiagrammatic flow sheetV of my
‘improved
process
and
.
75 - Figure'2 is a chart showing
‘
’
‘
the remarkable and
v
'
2,407,716
5
unexpected octane number and gravity charac
vided with a reboiler 29 which maintains temper
ature of about 250 to 450° F. at which tempera
ture the remaining light naphtha is Withdrawn
teristics of the `ultrane as distilled from virgin
light naphtha.
The light naphtha may be from any of the
crude sources above indicated, preferably from
.a crude which is high in light naphtha compo
nents. Instead of employing a virgin naphtha,
I may employ a hydrogenated cracked naphtha.
through line 30 to dehexanizer column 3 I.. ‘ A re
boiler 32 at the bottom of this column maintains
a temperature‘of about 300 to 350° F. and anin
termediate naphtha is withdrawn from this col
umn through line 33.
The top of the dehexanizer column 3i is main
Cyclopentene and cyclopentadiene as Well as cy
clopentane are formed in catalytic cracking and l() tained at a temperature of about 150 to 180° F.
in thermal cracking. On hydrogenation both of
at atmospheric pressure or about 280 to 300° F.
these cycloolefìns are converted into cyclopen
at 80 pounds gauge by suitable reflux mieans 34
tane. Cyclopentadiene boils at 105.8° and cyclo
which, as hereinabove described, may be cooling
pentene boils at 111.4° but pentadiene-1,3 which
coils or added reflux liquid. The overhead pen
has an octane number after hydrogenation of
tane-hexane fraction is the material previously
only 64 C. F. R.-lVl., boils between them at 108.5°
called “ultrane concentrate.” It is introduced
so that it is desirable to hydrogenate the cracked
by line 35 into depentanizer column 36. The
`products before fractionation rather than after
top of this column, is cooled by suitable reflux
wards. When cracked naphthas are employed it
means 3l to temperatures of 100 to 120° at at
is thus possible to separate cyclopentane from 20 mospheric pressure or about 230 to 270° F. at 80
normal pentane by hydrogenating the cracked
pounds gauge. Normal pentane is drawn over
naphtha before effecting the'distillation.
head through line 38.
Catalytically dehydrogenated light naphtha
The base of depentanizer column 36 is provided
may leave cyclopentane unchanged _or may par
with reboiling means 39 for maintaining a tem
tially convert it into normal pentane. Cata 25 perature about 150 to 350° F., depending upon
lytically dehydrogenated heavy naphthas may
the pressure, which temperature must be suffi
give appreciable amounts of cyclopentane result
ciently high to insure the removal of substan
ing from the simultaneous destructive hydro
tially all of the normal pentane from the hydro
genation of alkylcyclopentanes. Therefore, my
carbons which leave the base of depentanizer
light naphtha charge may be obtained from a 30 column 30 through line 40 to the Aultrane col
catalytic reforming process.
,
umn 4i.
My preferred charging _stock is a virgin light
naphtha from crudes containing 10 to 50% of
Reboiler e2 in the base of the ultrane column
maintains a temperature of 150 to 350° F.> Vand
branched hexanes are Withdrawn from the base
gasoline such `as Mid Continent, East and West
Texas, Pennsylvania, California, Coastal or cer
tain foreign crudes. This charging stock is in
troduced from line l0 by pump Ii through coils
i2 of furnace I3 and thence through transfer line
I4 to crude still or fraotionating column l5
which is provided with suitablereflux means I0
at its top and reboiler means l 'i at its base. The
temperature at the base of this “crude still” col
umn is preferably about 400 to 600° F. and topped
crude is removed from the base of this still
through line i0.
The temperature at the top of '
`crude still column i5 is preferably about 250 to
,350° F. at atmospheric pressure or about 35,0 to
of this column through line £3. Suitable reflux
means 44 at the top of the ultrane column main
tain a temperature of about 130 to 140° F. at at
mospheric pressure or about 250 to 280° F. at 80
pounds gauge.
Here the use of a high reflux
ratio is particularly important and We have found
lthat in. 10-«20 plate columns, the reflux `ratio
should range from about 50:1 to about 10021.
The ultrane overhead from column Mis with
drawn through line ‘l5 and cooler 55 to ultrane
Ol
storage tank G7.
-
. _.
With proper control of ilovv‘rates, tempera
tures, pressures, etc. in the fractionation system
as hereinabove described, the ultrane should be
substantially free from normal pentane and from
450° F. under pressure of about 80 pounds gauge.
The light naphtha overhead products are `with
-drawn through line i 9, through cooler 20 into de- ' a rnethylpentanes and normal hexane. If the frac
butanizer column 2i. Natural gasoline from
some outside source may be introduced intothe
tionation has not been sufficiently close,y l’ may
rerun the ultrane in either a batch still provided
with an eificient fractionating column and em
system through line i9 together with or in place
of the light naphtha overhead products above
described.
ploying a high reflux ratio, and by this means
obtain necessary sharpness of fractionation and
freedom from normal pentane and other unde
sirable hydrocarbons which distinguishes ultrane
from the .so-called close cut-fractions heretofore
obtained. Such rerunning is necessary in the
..
By suitable reflux means 22, which may be cool
ing coils but which is preferably introduced re
flux liquid, the temperature at the top of de
butanizer tower 2| is held at about 40 to 80° F.
at atmospheric pressure or 150 to 200° F. at 80
case of the rare crudes which contain unusually
pounds gauge. Butanes and lighter are taken
overhead in line 23. Reboiler coil 24' at the base
of debutanizer column 2| maintains a tempera
ture of about 200 to 400° F. at which temperature
debutanized light naphtha is Withdrawn through
line 25 to isopentane column 26.
The top of isopentane column 26 is maintained
at about 80 to 100° F. at atmospheric pressure or
210 to 280° F. at 80 pounds gauge by suitable re
flux means 27, which may be a cooling coil but
Which is preferably introduced reflux liquid.
The reflux ratio in this case should be relatively
high, preferably about 20:1 to 60:1. Isopentane
is removed overhead through line 2B.
The bottom of isopentane column 26 is pro
small amounts of ultrane.
The boiling point of the ultrane as above
stated should be about 120 to 124° F., its refrac
tive index (ND20) should be above 1.3800, pref
erably above 1.3900, its A. P. I. gravity below '75°
and preferably below 65° and its octane number
above 95 C. F. R.-R.
The isooctane referred to herein is the com
mercial product which may for instance be pre
0
pared by polymerizing isobutylene to isooctene,
then hydrogenating the isooctene to isooctane.
Alternatively, it may be prepared bv` the alkyla
tion of isobutane with butenes or by the dehydro
alkylation of isobutane. It may also be prepared
75 by destructive alkylation of higher branched
2,407,716
8
7
paraiiins. My invention does not relate specifi
cally to any particular methodV of obtaining the
about 10% of‘each of the following fuels wer
blended with a standard reference fuel:
-
isooctane but by this term I mean to include the
aviation motor` fuels prepared by the above or
.
fBlending
Hydrocarbon
any rother processes which contain substantial
octane
number
amounts of 2,2,4-trimethyl pentane, 2,2,3-tri
‘ methyl pentane and 2,3,4-trimethyl pentane and
' which have an octane rnumber' above 90 C. F.
Cyclopentane
___________________________ _ -_ _________ _ _
A120
Neohexane (2,2-dimethylbutane) ________________ __'____
2,3-din1ethy1 butane ____________ _.
99
___
K 112
R..-M. or above 9.0 octane number by any of the
Triptane (2,2,3-trimcthyl butane) ____________________ __
110
‘
98
10 Isooctane (2,2,4-trimethylpentane) ___________________ __
ordinary test methods.
The‘isooctane or equivalent product is with
drawn from storage tank 48 by pump 49 and into
The critical lcompression ratio of pure cyclo
blending line 50 While ultrane from tank 41 is
pentane is 10.8 as compared With only 7.5 for iso
withdrawn by pump 5i, line 52 and line 53 to
octane. With 1 cc. of tetraethyllead rper gallon,
blending line 50. I prefer to employ about equal
the critical compression ratioof cyclopentane is
parts of isooctane and ultrane but, as above
increased from 10.8 to 13.5 while that of isooctane
stated, my aviation super fuel may contain from
about 30 to 70% ultrane and from 70 to 30% iso
octane. The volatility and octane numbers of a
50:50 blend are preferably about as follows:
.
50% isooctane+50% ultrane=
Aviation gasoline
° F.
° F.
164
215
228
235
263
94 0. N.
119
121
122
123
125-130
100+0. N.
A
° F.
121
140
176
232
258
is increased from 7.5 only'to 9.8 with a corre
sponding amount of added tetraethyllead. Cyclo
pentane with 1 cc. of tetraethyllead is almost
exactly equivalent to isooctane plus three times
as much tetraethyllead. The critical compression
ratio of cyclopentaneis even superior to that of
such anti-knock hydrocarbons as ethylbenzene
and, of course, cyclopentane is markedly superior
25 to ethylbenzene as a blending agent for isooctane
, because of its high volatility, relatively high heat
ing value and stability. Furthermore, the addi
tion of tetraethyllead raises the compression ratio
of cyclopentane more >than that of ethylbenzene.
100:4;0. N .30 One of the outstanding characteristics of ultrane
is its effect in increasing the critical compression
ratio of the isooctane aviation fuel.
While ultrane is my preferred blending fuel for
use with isooctane, it should be understood that
`
While I have described in detail a preferred
embodiment of my invention-it shouldbe under
Y >I may further fractionate the ultrane to obtain 35 stood that various modiñcations and alternative
substantially pure cyclopentane. Ultrane, for
example, maybe Withdrawn through line 54 to
an- azeotropic distillation unit employing meth
anol or other Water-solubleA azeotropic agent.
procedures will be apparent from the above de
scription to those skilled in the art.
I claim:
'
'
'
1. A composition of matter consisting essen
The neoheXane-methanol azeotrope boils several 40 tially of cyclopentane and neohexane and con
Y
Ydegrees below cyclopentane-methanol azeotrope
taining about 30 to 90% by - volume of cyclo
When distillation is carried out under the proper
pressure. As a rule, such azeotropes can be frac
tionated more easily than the hydrocarbons alone
pentane which composition is substantially free
from normal pentane and which is characterized
by a boiling range of about 120 to'124° F., a re
due, in part, to the fact that the presence of the 45 fractive index above 1.38, A. P. I. gravity below
azeotropic agent increases the volume. While
75° and an octane number above 95 C. F. YR.-R.
azeotropic distillation is a preferred method of
2. An Iaviation super fuel whichY comprises
, obtaining the pure cyclopentane, it may be under- '
about 30 to 70% Aof the composition defined in
I stood that other processes maybe employed.
claim 1 together with about 70 to 30% of an iso
These processes are not an essential part of the 0 octane motor fuel having a 10% point of about
200° F. and a 90% point of about 230 to 270° F.
present invention and are therefore not discussed
in greater detail. Cyclopentane may be blended
3.' An aviation super fuel which comprises a
’ with isooctane to form aviation super fuels> in
the same proportions as ultrane is blended there
with.
»
' The value of the finished fuel may be illustrated
by knock tests at engine speed of 600 R. P. M.
with a jacket temperature of 212° F. The follow
ing blending octane numbers were obtained when
commercial isooctane motor fuel having a C. F.
R.-M. octane number of at least about 90 blended
55 with about 30% t0 70% of “ultrahe”
4. The aviation super fuel or enum 3 which
contains from about 1 to about 6 cc. of tetra alkyl Y
lead per gallon of aviation super fuel.
‘
ROBERT F. MARSCI-INER. ì
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