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2,404,452
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PRODUCTION OF AVIATION GASOLINE
Filed March 27, 1944
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InvenTor'. lIvcn* G. Nixon
Bg his A’H'or'neHLÈ .___
2,404,452
Patented July 23, 1946
AUNITED sTATEs PATENT OFFICE,
PRODUCTION OF AVIATION GASOLINE
Ivor G. Nixon, Ewell, England, assigner to Shell
Development Company, San Francisco, Calif.,` a _
corporation of Delaware
Application March 27, 1944, Serial No. 528,290
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. This invention relates to the manufacture of
when conducted by'iconventional methods, us _.
aviation gasoline base stocks by the cracking and
re-cracking of selected hydrocarbon .distillatea
ally cause the formation of large amounts of ole
iins. For this reason, thermally cracked naph-i
thas have not generally been used in aviationV
and especially to the art of re-forming low oc
tane naphthas to increase their rich mixture rat
ings in blends in super-charged aviation engines.
in
gasolines,
It is also known that for a given hydrocarbon
feed, a practical limit is placed on the attainable
vseverity of cracking conditions because Vof coke
deposition. There is a certain severity of crack
These ratings are expressed inV “index numbers”
which are obtained by calculation. fromv blends
tested at their detonation limited power outputs,
Research .Committee
ing above whichcoking becomes very rapid, and.
(C. F. R.) super-charged 3-C engine.4 The test
was carried out according to the Coordinating
Research Council method designated CRC-F-4~
ybelow which it `is very slow. .This critical value
may to some extent depend upon'the de‘sígnof
»143, and described in the report of August Vv2,
but for a given furnace it isa function of the
nature of the feed.` Sinceaçfurnace must be shut
in
a
Cooperative Fuel
the furnace inwhich the cracking is conducted, »
1943 of the subcommittee on Blending Octane'
Numbers of the Aviation GasolineA-dvisory Conn
, down and cleaned as'soonyas deposition `of'coke - -
begins to plug it, it is obvious >that only processes
mittee to the Petroleum Administrator for War.
Index numbers areapproximately equal to the
in which coking is relativelypslow are economi
cally practical. However, more severe cracking.
percent of power that the fuel can produce as
compared with the power produced by iso-octane 20 conditions can be maintained without objection- f
underthe same conditions.
able coking by any one or more of the following '
'
methods:v (1) introducing into the cracking zone,
together withV the naphtha, flow" boiling hydro»Y `
`carbonscontaining from“ 1 to'about 5 vcarbonat
“Index number” differs from “octane number”
in that the lformer is a >measure of the allowable
output of a super-charged aviation engine under
take-off and climb conditions while octane num 25 oms per molecule; (2) reducing the amount of Y
oleñns present in theïnaphthaLto-be cracked ;-'a’nd '
b_erv is a measure of the detonation tendency of
the fuel in a nOn-Super-Charged'engine under Y » (3) l.increasing-the aroma-tic content of the -frac
cruising conditions. Thus octane numbersand
index numbers referto very diiferent fuel prop
erties.
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tionto be cracked.y
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ì
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naphtha ,fractionsV having'ilow olefin content are
cracked and recracked under certain- conditions,
‘
It is well known that naphthas used inthe
blending of high grade motor fuels,` >and partic->
‘ a relatively high boiling fraction may be obtainedv
.that has a high concentration of aromatics, a low
ularly aviation gasoline, must have a high anti
knock value, must be free of gumeforming com
ponents, and must maintain their anti-knockv
properties under severe engine conditions, i. e.V
high temperature, high compression and rich mix
ture.
A
_ It has been discovered'that-if certain selected
concentration of oleñns and a greatly increased
index number.
‘
.
It is an object of the present invention to pro
vide an improved methodV for making aviation
" blending stockhaving a high rich mixture rating
For these reasons naphthasV rich in aro
in supercharged engines, that is, a blending stock
matic hydrocarbons and substantially’free from
olefins are preferred. Aromatics are known to 40 having a‘high index number. Itis another ob
ject to produce naphtha having superior anti
have excellent anti-knock properties which dol
`knock andy storage properties.' ‘ Another object is
not decrease under severe operating conditions
to provide a cracking process capable of» produc
and have' no tendency to form gums“ or to de
teriorate otherwise during storage.` Olefins, on
ing a naphtha having high aromatic content and »
the contrary, frequently oxidize and‘polymerize fr
unusually low olefin content from which ,purei
during storage, forming gums, and thus render a
motor «fuel less desirable »for airplane engines..
It is well. known that by suitable thermal treat- Y
ments 4Which may involve carbon-carbon scission .
, and dehydrogenation or isomerization or poly
merization or a com-bination of these reactions, it
is possible 'to increase the octane number andthe
aromatic content of hydrocarbon oils without
substantially changing their boiling range. At
the same time, however, such thermal operations,
aromatica' particularly toluene, may be obtained,
if desired. Still another object is to produce a
maximum amount of aromatics and high index 'I
number components from 'a >naphtha fraction‘
with a minimum amount of re-forming capac
ity.
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The process of this invention comprises the
lfollowing essential steps:
«
1. Thermally cracking a'straight run naphtha
55 having a selected boiling range;
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2,404,452
s
_
4 .
2. Fractionating the resulting cracked products
to obtain a'selected naphtha fraction; '
y
ing stocks or which yield such aromatics in the
subsequent cracking steps of the process. Ii’ the
cracking stock is very rich in oleñns, then the
product of re-cracking, that is the aviation blend~
Y
3. Rea-cracking said second fraction, preferably
Vin the presence of a light feed; '
Y 4. Fractionating the resulting re-crackedprmi-V
ing stock, will also be relatively rich in oleñns. ' .
`uctsto produce light aviation blending stock and
a relatively heavy ,Y fraction boiling essentially
Also more coke formation will be encounteredY
within about 140° and 225° C.;
caribe obtained in the process. ’,That this must be
which will, in part, limit the index number that
» .
5. Further re-cracking said heavy fraction,r
Vpreferably in the presence of a lightieed; and
avoided has -been pointed out before. '
Thus the boiling range of this starting material
Y ,_
6. Fractionating the Yresulting cracked heavy'Y
“lies in a range essentially within about 96°. and
Vfraction to produce a heavy Yf,aviatio_nY¿bleriding-->
Y stockof high index number.
"
'
230° C; If the boiling range is high, say essen-k
tially within about 150° and 236° C., an increase
'
be inserted between'steps'4 >and 5' a treating stepY
wherein both Ythe lightandheavy fractions are
in the, yield of the heavy aviation blending stock Y
`is obtained/.at the expense of a decrease in the c
,yield of the light aviation blending stock which
v
treated vto »remove small.V "quantities 'ci .olefins ,
maybe removed between steps ‘l and 5, men- f '
.r 'In addition to these essentialv steps, there'may
f Which’maybe present before they Yare' separated. . .
f, Further, Ithe iinalheavyraviation base stoc’k‘may
be fractionated andtreated to improve its avia~VVV
ti-onblending characteristicsz‘
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ï>
Y,
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«-.»‘ÍTl`iermalf’~’=V `rcracking vmeansV non-catalytic
cracking. o'rïcracking in the.A absence-oi"~ a catalyst
"asun'derstood in theV conventional> sense, in »aocordance with the accepted usage in the prior art
tioned above. For example, if .the initial boilingpoint ofthe starting material is above theV boiling
point of toluene, say at about 1l9° C., then the
yield of vthe heavy aviation blending stock al
most twice that compared` to the yield- obtainedk `
' from a starting material having an‘initial- boilingVVV . Y
point at §5° Cland includingïtoluene, While the
total yieldofrrlight and heavy aviation ’fraction ’
as exemplified. by the deñnition found onY page?!
, remains about the same.
of‘fThe, Chemistry ofV Petroleum DerivatiJzes’Í-‘by ,
y In the» ñrstrstep of thisV process, the selected
Carlton Ellis, publishedin 193s.
The .success oiìrtheV present*k invention, and! par-_ `
ticularly ofx'the re-cracking, ¿dependsy onîV the ~.
properl selection ofrthefstraight run'v andr the.'
crackedénaphtha fractions. 'It is only` when alli
1 three' ofgthesefractions are-properly chosen
crackedrunder the proper.conditionsfthat the full
beneñts of ¿this inventionareï obtained.. ’ -
lfllhe. natureVV of 'the .invention willV be better un- t
. r
1 ‘~
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straight run»_` naphtha fraction .is introduced»
throughline l tintov a cracking zone sucha'sïa
crackingcoiliä whereinrit is cracked in a pseudo
, liquid phase,l (that is,"l~cra`ckedl above the critical
Y temperature and pressure 'of-. the naphtha-frac-ï
tion) ¿under conditionsvas severe as ispractical
withoutexcessive‘ coking.> Il» desired, the time off
vcracking may be extended andg'controlledi with
theuaid or” a reaction> or soakingY chammr notiV
derstoodefroin thedfolloivingdetailed description, »v shown.Y Forrinstance, these crack-ing conditions
~ , taken. together with the' drawing: forming` apart ~
Y Qfllthis. specification., .This ‘drawing presentsY ar
of. a `preferred embodi
Y simplified. flowdiagram
'
mentofthe;invention.-
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For; simplicity/riY the.“ drawing . doesßfnot show»,
. pumps, vheat:.exchangers> valveabyëpasses, vents, »
have been> found` to- correspond- to lcrackim'g »tem
peratures'between-.about 5409 C.V andë580°
and; v
inlet pressures between# about 54€) and Yi100;
Lrg/sq. crn.
Y
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Y
Y
ln >the secondV step, the resulting cracked prod- kj ~
@ucts froml'zone ¿Klare Wíthdrawnthrough line,- 53'2
and» are quenched` and fractionallydistilled in the
‘ reboilers, '"condensers, and 'otherÁauxiliariea Ythe
proper ,placement- of.; which ,willvv at=-fonce .be evi 45 distillation column Zi‘lto separate therefrom those
dent tdthoselskilledin theart.'
products boiling aboveabout 230° C. and preferl- '
Y 11:? Therst‘raight runchydrocarbonl ¿napht a. which' >
forms the starting material of thepresent process
ably above Zûû‘îf C. whichY are Withdrawn from thev '
bottomof the column 2li through line 2 l. The
maycoriginateïi‘rom, anyçcrudaßthoughÍaromatic
remaining lighter portion of the products »is With- '
Floriinstance, a. 4straight run: 'naphtha‘ fraction
having.' a _U.„;O. lE...characterizatio'ni.factor Vbelof-.xz
tion column
or naphthenic.' oils are :preferred=.to.p‘arañir1icones.' 50 drawn from the top of the column through line? 22- K '
~ Y1.1;6 . andi preferably. below, 171.4; is.' preferred. ,ì The
andfintroduced into another fractional distiller-_
wherein- the, products boiling Vbef
low about $0", Grand-»preferably belowY about-¿193°l
U. O. l?. characterization. factor is Aacm'easureloi`the parafûnicity of an oil. A highly paraiiinicjoil 55 of. columnlrZä.V rThe remainingfraction,` which;
hasa, factor„of,=l2.5_ and aA highly aromatic and;
has a boiling range.essentially-within aboutQGîTC; '
naphthenic Yoil has a> lovverf‘actor .approaching li)
and< 230€’. C. ’will be -referred to hereinafter» as thel
asça, minimum.
i See. “Characterization of. l’petrvoe'f `
“second naphtha fraction,” and is?` withdrawn
leum f_ractions’.’ by Watsonghlelson:Murphy
fromV the bottom of` column 25 through vline Z-‘llï
,oi/U, O. P,.,'I¿nd, 'and Eng.` Chem., vol..2"!', l§lo„~l2, eo lTheY ,'gases.V and 'light hydrocarbons Withdrawn
`‘135.14.60...)
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; Furthermore, this 'starting `material` orfiirst
naphthafraction should p_l‘eferably have an *AQ S.
Y ` from the topfof. column 2,5,throughilinel2ä mayv
4'be separated rand employed in other processes’.
For example, the C5 and lighter hydrocarbons ‘may Í
Y 'Il-'_fl‘v/Luinitial boílingpointpf, not below Soi C. and
--preierably notbelow 190,? C. „ its end boiling. point
line, or, any C5 orhigher hydrocarbons. maygbe
distillatiûïi Shouldbe below about
employedas a blending. stock formotorífgas'olines
if desired. The C4, hydrocarbons mayV becohvertedl
¿and preferably belowy about 290° C'. The
reasonsforthese limitationsare asY follows: h_rst,V
most of therihyvdrocarbons boiling youtside »these
be alkylated to producea blending stock for. gaso-V »
into octylenes, cracked to produce.- butadiene, 'on
Valkylated to produce aviation blending stocks.
limitstend upon craclfnng to4 produce' relatively 70 The C3 hydrocarbons may be. chemically treated'A
large amounts of oleñns boiling within the boiling ' toproduce. acetone; and the. C1y and (lajhydro-k
range of, the cracked naphtha> selected.;for.` the
carbons maybe employed. as'fuel. Still further, _
'subsequent cracking steps andïsecond, that this
thehydrooarbons having `from 3.to»5.carbon atoms
fraction contains most. of ythe'.ar.ornatic hydrocar
per moleculemay beemployed again inl this proc.
v bons which are valuable for.l aviation'fuel blend 75 essasthe light feed that is preferably introduced
2,404,452
5
into the next two cracking steps as described be
low.
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This sec ndy naphtha fraction usually hasan
octane number of at least 74 or '75, and can be
used Vwith advantage as a motor fuel, but not as
aviation fuel. It is characterized by a relatively
the second operation. In the third cracking op
eration, the change in boiling range is less sige
niflcant because of its `relatively high aromatic
content.
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Another way of determining the severity of
cracking includes methods of determining the
aromatic content of the cracked product. Some
highlcontent of monocyclic aromatics and naph
of the ways of measuring this aromatic content
thenes, asV opposed to naphthas boiling above
'are as follows:
v
about 230° C., which contain a relatively large
One method is by measuring the change in
amount of polycyclic aromatics and naphthenes. 10
These latter compounds should not be included in
the selective fraction because upon cracking under
severe conditions they tend to promote coke for
octane rating of the fraction after it is cracked.
In general, the octane rating is determined for a
debutanized fraction having an end point of 200°
mation and lower the quality of the final product.
Moreover, as pointed out before, relatively high
boiling hydrocarbons tend to form large amounts
of oleiins upon cracking, which boil within gaso
produced in the process of this invention should.
preferably have an octane number of vbetween .74
line boiling range. .
Y
Y
_
By further treating this second vnaphtha frac
C. For example, the second naphtha fraction
and 78 by the C. F. R. motor method.
`
Y
Another method is by measuring the aromatic
content by percent by weight of the cracked prod
tion as described below, its octane number can be 20 uct which is extractable in 98% sulfuric acid.
aviation fuel.
This method is not very accurate, because >the
strong acid tends to polymerize some of the ole
ñns, causing them to remain in the oil phase.
However, if the bromine number of the cracked
through lineY 3|, wherein it isre-cracked under
aromatics present in the cracked product.
greatly improved, its aromatic content increased,
and itsparaflin, naphthene, and particularly ole
iin content decreased so that it can be used for
" AIn the third step, the second naphtha fraction 25 product is below about l0, the weight percent
extractable is within about 5% of the amount of
is introduced into a second cracking coil 30
A more accurate method is by means of the
conditions similar to those maintained in crack
specific dispersion which is a measure of the
ing zone I0. It is desirable, although not neces
sary, to add to this second naphtha fraction, 30 percentage of aromatics inthe resulting product
(see Ind. and Eng. Chem., vol. 29, No. 3, March,
through valved line 32 before it enters zone 30,
1937, .p11 319-325). For example, a fraction
a minor amount of light hydrocarbon feed con
which has a specific dispersion of about 135 con
sisting essentially of atleast one hydrocarbon
tains at least about 50% aromatics. ' Thus, the
having from l to 5 and preferably from 3 to 5
selected third naphtha fraction obtained from
carbon atoms per molecule. The amount of the
the products `of zone 30 should havea specific
light feed employed as previously indicated is
dispersion of at least about 135 and preferably
merely sufficient to reduce the speed of coking for
economical purposes, and otherwise has no ma
terial effect on the properties of the selected
‘cracked naphtha fractions. This amount mayv
rvary between about 5 and 30% and preferably be
tween 5'and 15% by volume of the feed to zone
‘30.
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at least about 140.
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It is essential that each cracking operation de
scribed in this process be carried out as a sep
arate step. If it were attempted to maintain
cracking conditions sufficiently severe to produce
the desired result in one operation without inter
mediate separation of light and heavy compo
The re-cracking operation in zone 30 should be
conducted under the most severe conditions which 45 nents, heavy and tarry components produced in
the initial stages would cause rapid coking in the
can be tolerated without excessive coking. These
`first cracking zone I because many components
subsequent stages. Moreover, the light unsatu
rated components formed at the beginning would
resulting . recracked products are withdrawn
v through line 33, quenched, and fractionated as de
are removed through bottom line 4| and the re
conditions may be more severe than those in the
be present in a large concentration, would poly
of the original fuel, which tend to decompose
readily, and cause coking, have been cracked in 60 merize to form oleñns boiling within the naphtha
range, and thus would produce finally a more
the ñrst cracking step and eliminated in the frac
unsaturated naphtha, which is not desired.
tional distillation columns 20 and 25. The con
In the fourth step, the cracked product from
Vditions correspond, for example, to temperatures
line 33 is introduced into the fractional distilla
ranging between about 540°-580° C. and pressures
ranging between about 40 and 100 kgs/cm?. The 55 tion column 40 wherein the products boiling
above about 230° C., and preferably above 200° C.,
maining portion is withdrawn through top line
scribed in the second. step.
42 into the fractionating column 45, wherein the
The severity of the cracking may be defined
either by the crackingV conditions, or by the 60 lighter hydrocarbons boiling below about 90° C.,
and preferably below 100° C., are> withdrawn
changes brought about by these cracking con
through Vapor line 46 to produce the “third nap-y
ditions in the properties of the hydrocarbon
tha fraction” which is withdrawn through bottom
and particularly in its boiling range. The
line 41.
latter method is particularly applicable when
This third naphtha fraction has an olefin con
the feed stock has a relatively narrow boil 65
tent much lower and an aromatic content much
ing range, because in such a case, portions
whose boiling ranges are changed are most
likely to boil outside the boiling limits of the
higher than that of the corresponding fraction
obtained from the products of the first cracking
zone l0. This third fraction should have an oc
feed. When deñned according'tothis method,
'the cracking conditions which, for this process, 70 tane number, by theV C. F. R. motor method, at
least 5 points higher than the second naphtha
'are such that a cracked fraction having the same
fraction present in line 21, and preferably should
boiling range as the naphtha feed amounts to
have an octane number between about 80 and 85.
about 50% to 90% of the cracked products in
It should be between about 50 and '75% by weight
'each cracking operation, and preferably about
„70% in the first operation and about 60% in 75 extractable with strong sulfuric acid and ~s'lioi'ild
2,404,452
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haveaspecific'dispersion of atleast 140 and 'Vpref- -
f A portion of the third'naphtha fraction (treated
or untreated, and/or containing toluene or not)
AIn a preferred, although not »essential embodi
may, however, be removed from Ythe system
ment of this process, the third naphtha fraction
through valved line 59 and employedras an avia
' is subjeeted'to a refining treatment. Thus, as Cl tion blending stock, in that it now‘h'as an' octane
illustrated yin. `the drawing, thev third naphtha
number between about 80 and 85 and an index
erably lï50Íorabove.
a
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` ‘_
’ fraction from the bottom' of îcolumn 45 is passed
through lines >«il and’5l to a treating unit'äû.
number, in a blend with 4 cc. of tetra ethyl
lead/gallon, between about 125 and 135.
The type of treatment employed depends large~
ly upon the properties of the third naphtha frac
tion. For instance, if `this fraction 'should con
Continuing the operation ofthe process of'this
invention, the untreated, or preferably the treated
tain'considerable amounts of oleiins, a treatment
ating column 60 Vthrough -v‘alved line 6l, `where
inïit is separated into a light aviation base stock
thirdna'phtha fraction i'spassed into the fraction
V‘adapted to'remove ithe ’major part'of the oleñns
is preferred. ' Such a‘treatment, for example, is
, a light sulfuric acid treatment.
and `a heavy fraction. The’ out point for this
separation may range 'essentially> within about
140° and 155"y C., but preferably whereinthe
Although a sul
furie acid 'treatment is known ordinarily to re
duce the octane number of cracked gasoline, it
does, on. the contrary, further raise the octane
number of the third naphtha fraction prepared
xylenes 'and eumene which have high index núm
bers, pass overhead into the light aviation baseV
stock (for'instance, at about 150 or 152° C.) . This
according to this invention. 'A suitable sulfuric
acid ~treatment lmay involve the contact of the
light aviation base `stock is withdrawn through
vapor line 62 and if desired may >be .further
treated or may be blended directly into aviation
- fraction with between about 1 and 5% by volume
of a "95 'to 98% sulfuric'acid. The acid employed
in theztreati'ng may be fresh 'or V‘may be spent
or yother motor fuels.
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.
Y
The light aviation base stock should have an
' Other treatments which may be employed in 25 octane number by the C. F. R.> motorvmethod
between> about 80 and 85 and should havean
the treating `unit include for example passing
index number in a blend with 4 cc. of tetra ethyl
the fraction over adsorption agents such as clay,
alkylationacid.
,
w.
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'
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lead of between aboutl 130 and 140.
bauxite, fuller’s earth, diatomaceous earth, sili
Between
ca.- gel, etc., vat elevated temperatures below in
about 50` and 75% of the light aviation base stock
of suitable concentration toV produce a sludge con
tainingthe undesirable constituents which can
and it should have a, specific dispersion above
cipient cracking; contacting with phosphoric acid 30 should be extractable with strong sulfuric acid,
about 140 and preferably above 150. The boilf
ing range of this base stock may lie between about
90 and 155c C. and preferably between 100 and
. be separated; selective hydrogenation in the pres
ence of a-suitable hydrogenation catalyst, suchl as
l5ü° C., although its end boilingr point‘may be
Vfinely divided nickel, chromium oxide, molybde
num or tungsten sulfide or a combination of
as low as 140° C.
these, etc.; treatment with catalyst of the clay
The heavy naphth'a fraction Withdrawn from
the bottom of column 6U, which hasa boiling
range essentially within about 140 and '230° C.
and preferably essentially Within about 150 and
'200° C., usually has an octane number by the
C. F. R. motor method within about 80 and`85,
type'under conditions which do not cause sub~
stantial cracking; destruction or removal of
harmful sulfur compound by -doctor treatment,
extraction with alkaline Vsolution in the presence
40
of a solutizer for mercaptans, lor oxidation -in the
presence of copper catalysts, etc.
The specific conditions involved in the treat
obtained from the book, “Chemical Refining of
tween about 1-10 and V125.
this book are descriptions of processes for the
Chapter II), with alkaline reagents (see Chapter
IV), sweetening processes (see Chapter V), re
ñning by adsorption (see Chapter VI) and relin
aviation base stock, in that it has/a specific dis
_persion of-at least 15€) and preferably aboveand
it is between 65 and 95% extractable with strong
,
'
,much lighter than treatments which would have
to'b’e applied to conventionally cracked naphthas
lor to the naphtha obtained in the iirs't cracking
60
Y
desirable, but not necessary, t0 introduce Ywithr
the'heavy fraction in line 63 a light hydrocarbôn
between about 5 and ~30% by volume, and pref
erably between about 5 'and 15% by voluineof ’the
'bottoms from the rfa-distillation are usually high.Y
If desired, the untreated third naphtha frac
feed'to cracking zone 170.
tion, or the treated andre-distilled naphtha frac
tion may be withdrawn through Valved lines y¿il or
5I and 52 to the toluene recovery plant 53, where
in toluene is extracted and withdrawn through
¿Valved line 54. The remaining non-toluene por
. tion of the third naphtha fraction is .returned
4to the process "through >valved line 58.
„ „
r3 t‘o 5 carbon atoms per molecule. The -amount
These 65 -of this added light hydrocarbon should range
-ly aromatic and may beblended into fuel oils.
.
,
In the ñfth essential step, the heavy fraction
withdrawn from the bottom of columneûû »through
through valve line "i2 consisting essentiallyiof at
least one hydrocarbon having preferably from
The treated naphtha may be'redistilledin col
umn 55 to remove higher boiling constituents
formed during the treating operations which
are withdrawn through "bottom line 56.
sulfuric acid.
lines 63 and 'H is introducedrinto a third'crack
ing coil lû. As in cracking Zone 30, it i's'also
step of this process, in order to obtain a product
having the same color, stability, low degree of
The aromatic-con
tentof this heavy fraction from >the bottom of
column 60 is much higherthan that of the light
treatment of hydrocarbons with sulfuric acid (see
unsaturation and low mercaptan content.
,
top of column 6B. Thisheavy aviation `base-stock
usually has an index number ranging only be-V
In
These treatments may be relatively light, i.‘e.
.
but its index number in a blend with 4 cc. of tetra
Petroleum,” vKalicl'ievsky and' Stagner, published
Ving with a solvent (see -Chapter VII).
`
ethyl lead is usually much lower than «that of
the light aviationfbase stock withdrawn from the
ing processes as above mentioned may be readily '
by Reinhold Publishing Corporation, 1942.
,
70
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It is possible, 'but not preferred economically,
-to employ the treated third naphtha fraction
from :line el as the feed to cracking zone Tllby
>by-jpassingthe column `60 >through line 13.
The cracking in zone ‘lil is generally'carried
l‘out 'under substantially the same coi-idi'tionsy as
‘those -employed 'in Àzones H1 and 30, although
v
,
9
_
f
Y
_
12,404,452
.
the pressure may be higher, if desired, ranging
etc. Many of these blending agentsmaybe ob
tained or produced from the -icy-products o'f'this
between about 40 and 95 k'g./sq. cm.
In the sixth essential step, the resulting cracked
heavy fraction Vis introduced intoV a fractionating
process.
._
__
»
It may be noted that the described process pro'
vides for the manufacture of a'superior aviation
column 80 through line 8| from cracking zone
10, wherein the products boiling above about 200°
base stock and valuable products from naphtha
C; and preferably above about 180° C; are with
fractions of relatively little value. '
drawn through bottom line 82. The lower boil
ing fraction withdrawn through line 83 is dis
_
~~
_.
The'follo’wing comparative examples illustrate-
tilledin fractionating column 85 to produce a 10
hydrocarbon 4fraction boiling below about 100°
C. and preferably _120° C.l withdrawn through top
'A straight _run naphtha fraction having ythe
the
.
.invention:
Example
> .
I
_
-
'
,
_
vapor line 86, andan intermediate fraction with
properties `disclosed in the table lbelow lwas
drawn 4through bottom line 81. This Vbottom
cracked in a iirst cracking zone having atransfer _
product is a vheavy aviation base stock usuallyV V15 temperature »of about 548° C. and an inlet pres
having an octane number above about 80 and an
sure of about 51 kg./sq. cm. to produce a cracked
product which was fractionated to obtain a sec
index number in a' blend- containing l‘1_-cc. of
tetra ethyl lead/gallon,»between about 150 and
165. The index number range is considerably
ond naphtha fraction having the properties 4dis
closed in ¿the table below. This second naphtha
higher than the index number of the light avia 20 fraction and a mixture of C3 to C5 cut amounting
'tionîbase'sto'ck removed from the _top of column
to about _14% of the feed was then cracked'in a
>(il), orthe third‘ naphtha fractionfremoved from
line 59 or the heavy fraction in line 63.
'second cracking furnace having a transfer tem
perature of about 5419 C. and an inlet `pressure
of about 63 lig/sq. cm. to produce a re-cracked
,
vThe lighter hydrocarbon withdrawn through
lines-’46 and`86 _of columns 45>`and 85 may be
ïiìoinedfwith those> _from the top -of ‘column 25 in
Y product which was fractionated to- obtain a third
V'line 26 and separated for use in the same manner .
in the table below. 'This third naphtha fraction
Was then acid treated with about 2% by weight
of 98% sulfuric acid and re-distilled to remove
A‘a's‘ï those described from line 26.
` "
naphtha fraction having the properties disclosed
'
'_ ¥~ The heavier fractions withdrawn from vlines 2 I,
- 4l »and r8i of columns 2U, .'40 and 80, respectively, 30 lanyA high polymers formed during the acid treat
_are highly aromatic and may be blended, if de
ment. This treated fractionwas then further
si'red,_'i_nto fuel oils or used for any other suitable
fractionated into a lightl aviation Vbase stock and
purposes.
_
Y
_i
a heavy fraction having the properties disclosed
The heavy aviation base stock maybe With
in the table below. The resulting heavy fraction
drawn from the _system through valve line 88 or
and aV mixture of C3 and C5 gases amounting to
it may be _subjected to treatment similar `to that ,
about _11% of the feed was-_then passed through
described for treating unit 50. If the heavy
a third cracking furnace vhavinga transfertem
ibase stock is treated, it is passed through valve
perature of about 545° Q. and an inlet pressure
"line 89_ into thetreating unit 90 and then passed . of about 76 kg./sq. cm. to produce a cracked
vinto the re-run column' ¿95 _similar to column 55. 40 product which was fractionated to obtain a heavy.
Thistreatmentof the base` stock does not ma
aviation base stock having the properties dis
teriallychangeits octane number orits index
closed in the table below.A
Straight
.
'
I
Light
Heavy
rltiln!1 nssf’gää‘lia n'äääga avliation
tHezìvy
aviation
fralîztion traction fraction
stock
, _
stock
na
"
‘
'
‘ l
f
.Speciñc gravity ____________________________ __
. C
t a
0. 786
A. S. T. M.:
f
'
I. B.
’F. B. P _ _ _ _ _ _ _
120
77
_-°C__
._°O_-°C__
134
157
210
, 123
146
209
_ _ _ _ _ _ _ _ ._°C__ __________________ -_
'Bromine number;- ______________________ __
._
(Reed.) vapor pressure ________________ _.
Octane number (clear, A. S. T. M
\ .
Y
0. 824
0.805
0. 844
110
97
146
_ 130
121
139 .
166
108
117
138
154
160
170
148
157%
169%
152
179
180
` 25.4
6
18
49
60
.8
V1. 2
75.8
81.5
80.5
_
y
6%
5
53
69
,
`
motor method)- __________________________ _..
Index number (in blends containing 4 cc.
llnarblend. y
_
. 0
0.858
_
'
129
180
4
__ 86 -
0. 3
.
52.6
`
TEL.) ..... ..`-'. .......... __f_'.' ________________________________ _-
. niimbergfrom what it;
ase
~
--°O-_
`>Percent byw.extractablew h98% HzSO4
~`
‘ ^
rac lon
P34.
`
10%50%.
90% ____ ._
‘
0.807
ase »
'
0. 4
83.5
‘90
119
157
`
136
.
as before the Ltreatment.
60
f__f ‘__fI_'h__e_ _treated vproduct may- be withdrawn _from
fthe top of vcolumn l95. throughyalve line `9_6 ,or .it
`'may be _passed _throught valve line _9,1 `into a blend
"ing- plant _^ I_.ûßiwhere?itLisi mixed with _other base
_stocks to produce _a finished aviation gasoline.`
is materially above that of the third naphtha
fraction or even thelight aviation base stock.
Furthermore, it may berseen that the high boil
f >ing range of the heavy aviation base stock lends
jSome suitable Vblending yagents ` toV `produce >a
7iinished aviationggasoline include light straight
run gaso1ines,_`isopentane, cyclopentane, neo
itself well forÁblending with iso-pentane andfsirn
._ ilar volatile blending stocks. _
'
„
i
Example II
' hexane, '2, Bedimethyl butano, di-isoprop-yl ether,
triptane, iso-octane, alkylationgasoline produced
From the above tame, it may Vte' yseen that the
index_number of thel heavy aviation base. stock Y
70
Another sample of a heavy fraction which had
" by reacting isobutane with" C5 and lower oleñns,
been cracked, fractionated, re-’cracked and fur
_ etc._ These blendingagents give the proper boil
ther fractionated as described in Example I had
the properties shown in the table lbelow. A feed
ing range tothe final blend and _its octane num
‘jbe'r may be ¿further improved by the addition of
»tetra-#ethyl lead, aromatic mono-cyclic amines,
consisting of this heavy fraction contained 13%
j by volume of a light hydrocarbon feed consisting '
_
Öl predominantly of propane ._andnpropylene, vbut j
î ,also including soniei'C'i; and> Cs' hydrocarbons, was
Y
f
12
Y
l
fingf ¿the resulting ¿re-.cracked .product ¿bye itself :to
1 produce a heavy fraction-boilingfessentiallyiwitl'lin
ì `ture* of ab.outv540°_C. and an inlet ¿pressure Vof 76
:midrange _oiabout `.140° «,C.l:and.r230°:.C.,;turther
-non-catalytically crackingsaidheavy'v fractionziin
Y; thenfractio-nated toob'tain a heavy'aviation gas
Vconsisting >essentially o1" at: least k:oneghyfdrcc'arbon
î further cracked in a cracking coil ata tempera- i
¿1kg/sq. cin. ' The resulting 'cracked ‘product »was ,5 fthe'fpre'sence of `a minor amount iof: a light’ffeed
havingA from §13 ltori 5» lcarbon-zatorns Vper finolecule,
i >oline base stock having> the ,improved properties
.separating thegresu'ltingi further ci‘ackedmrodguet '
It shouldV be .g noted '
Y l ¿shown inthe table below.
byitself to produce: an aviation¿'¿basexstockiboil~
ing; essentially ywithinf the -range `of ¿about ¿100°`
that the index number of the- heavyY aviation f
' i base stock is better than iso-.octane containing
î4 4 cc. tetra ethyl lead. The resulting cracked'p'rod- "
l yuct wasthen fractionated to obtain a heavy avia-V
` .-tion gasoline lb_ase .stock having` the ’improved
"fpropjertiesshown Yinthe 'table below.V
'
Y
Heavy
'„gaand100kg/saam.
.
-
.
'i
.A
„i
.
..
¿volumegoflthe îfraction being-cracked.
_
avlationf
.fractlonr
.
f 6. >TIT-he process of ìclaim-5,` wherein theiamount
Heavy
_
~
«and 200710.., each ofcsaidcracking operations-being.
yconducted ,iatgartemperature'r between. about; 540°
base stock
n .'7. 'The> 'processoffclaim’ì whereinîfsaidi-light Y
`feed is between about 5%1-anri'l5%.byf:vclumeïzof
Speciñc'gravity _____________________ _ _
Y
»
1504 ___________ __
__-
;
l0. 8,47
0. 858
»149
133
155
1,6
148
l5
174. 5
186
170. 5
184
14. 7
8. 5
68
87.0
`
y20
Octane numbericlear, A. S. 4T.,M.-vC. F.-R. motor method)____
'index number (in blends, c
Y
`'l"EL)K_______._.
_._‘__
’
~83. 5
t ming 4
,
- .
in the range of ~about"90°C„;»and 230°„-C_.,¿non-catalytically Vre-cr.acl«:ir~1g said y*second '.naphtha
Above‘l54
separating the resulting re-cracked'.
13o fraction,
product by itself to produce awthird naphth'affrac
i `I claimas my invention:
-tion boiling essentially withinthefrangeof about
._1. Aprocess forîproducing anaviation gasoline i
100° C. and 200° C., further separating said third
,naphtha fraction `vby itself «into» aY light îaviation
basestock.l from la straight-run naphtha having a ‘
boiling range; essentiallywithin about 90° C; and '
¿
'
, second naphtha‘ fraction boiling essentially 'With- '
91:3
Y
.___.__-., ____________ ._
1
lytically cracking said naphtha, sepa-rating'the
resulting crackedp-roduct by itself- to‘pro'duceîf'a
v25
Y
_
à~8. ,A ’process for producing.¿anfaviationfgaso
line base stock from a- straight runinaphtha »hav
ing a boilingrangelessentiallyfwithin about 90°
C. and=230° C., comprising theqsteps of none-cata
`(Reed.) Avapor pressure___; ________ __, ........... _____ ....., ...... __
i
the ~vfractionfbeing cracked.
Y
Y
`35
230°.C;, comprising _thestepsof
ncnfcatalytically
base rstock boiling -essentially vwithintheY range
; .cracking saidnaphtha, >separatir-ig the resulting> . of about 90°C. and l,155° C. anda heavy fraction
boiling essentially within the range of about,1v40°
l ~cracked Íproduct by itself >to produce .a second
ï -naphtha fraction boiling essentially :within‘_:t‘neV f C. and 200° C.; furtherlnon-catalytically cracking
/said heavy fractionfseparating the resulting ,-fur- 'V
Q rrangeofiabout90° C. 'and 230° C., nonscatalyti
1 ¿cally 17e-cracking said .second naphtha fraction,` .i0L ther crackedproduct by »itself _to .produce .an
Y"separat-ing _the resulting :re-*cracked product-,by
. aviation base «stock lboilingïV esentialli7 _within lthe Y Y
mangent about .100° C..fand 200°fC.,¿each¿of.îsaid '
‘ >about 140° c_and abouezßo" _0., furtnernoßncata- Y ' „cracking Aoperations „being conducted at a tem- ¿
perature between about 540° C. and 580° C. and at Y
lytically cracking said heavy fraction and separat- `
Aing i the resulting «,further~gcracked 1product by it» 45V a pressure between about 40 and 100 kg./sq. cm.
`
itself to produce a heavyfraction boilinggbetween
self to produce
9. A process for producing an aviation gasolineV
aviation base stockkgb‘oiling
hasezstcckrfrcm astraieht run 'naphtha having>
essentially within .the vrange ._ofabcut _1.00° _Q. i and
a boiling range v.essentially within about 90° C.
conducted at a temperature between about §540° " and 230° C., comprising the steps of non-catalyti
gC. and i5180° C. ¿and at a pressurebetween about 50 vcallycrackingsaidnaphtha, separating the re
',sulting cracked product- by itself to produce a
¿40 and 100 kg./sq. cm. '
‘
.20.0° C.,._each.of.said cracking-practices being
second naphtha .fraction boiling essentially with
‘2. The process of ¿claim 1,-wherein the `firsty
cracking operation is conductedunder »conditions
in the range of about'90°'C. and 230° C., non-cata
v@lytically¿refcracking `.said second naphtha frac
to yieldazgacoline having an octane number above:
. about El7_4: _and said second crackingroperation -is
Ation('inlthe.presenceof -a minor amount of a light
ffeedV consisting V.essentially of at least one hydro
, conducted to yield agasoline having ‘an octane Y
*numberßabove about 80.
_
Y
` ,Y
carbon >havingfromvß to 5 carbon atoms per
"
molecule, »separating »the resulting Y1re-cracked
>3. The .process of claim.lfwhereingthe.naphtha - _.
Vproduct by itself to produce a third naphtha frac-V`
fractions boil essentially within the range of f
‘
"about.100°`C.„and_200°C..
tion boilingessentially .within the rangeïof-about
'
_ l. _4, 'Theîprocess of claim Lev/herein,saidgstraight-È "
_run A naphtha fraction has , ar U. .0. „ Pjcharacter- §
`
_iz?ltiongfactor below
11,6.4
~
i
l.
` Y _100° „C. v and 200° C.,.furtherseparatingßsaid third
l ¿fraction ioy-îitseifA _into a. iight aviation base stock: 1
l i'V
_15. l._A process for producing an _aviation gasoline.:
"boiling »essentiallyiwithin the range .of ` about 100
base stockrfromastraight run naphtha .havínslaî
boiling range Ywithin ,about .90° _C. A_and 230°_„C.,'
tiauywithin 'thefrange of about v150° aandzoo‘?
i . fraction'boiling essentially within the range *of> 70
molecule,-and separating the >resulting further
C., further non-catalytically- cracking ysaid :heavy „
comprising the steps >of‘nonecatalyticrally cracking.:V - Afraction in thepresence -of a minoramount gof'a
saidv naphtha, separating the resulting cracked
light feed consisting .essentially of at ¿least one
product by itself :to'produce a second-naphtha
`hydrocarbonhaving from 3 tov 5 carbonatoms per
about A90° C. and :23.0° C.; non-catalytically lre
cracking saidsecond naphthafraction in the pres
crackedproduct by itself to produce a heavy avia
‘ » ence of vaininoramount of a light‘feed consist- 4
Ytion base stock boiling `essentially within ¿the
range` of about„l00°»C. Vand 200° C., .each of said
-ing essentially of atleast one hydrocarbon having
.from 3 to 5 carbonratoms -per.molecule, separat
ature between about 540° .C- and 580° C... and at
cracking operationsbeing conducted at a temper
2,404,452
f
~ 14
13
14. A process for producing an aviation gaso
a pressure between about 40 and 100 kg./sq. cm.
10. A process for producing an aviation gaso
line base stock from a straight run naphtha hav
ing a boiling range essentially within about 90°
C, and 230° C., comp-rising the steps of non-cata
line base stock from a straight run naphtha hav
ing a boiling range essentially within about 100°
C. and 200° C., comprising the steps of non-cata
lytically cracking said naphtha, separating the
resulting cracked product by itselfk to produce a
second naphtha fraction boiling essentially Within
lytically cracking said naphtha, separating the
resulting cracked product by itself to produce a
second naphtha fraction boiling essentially with
the range of about 100° C. and 200° C., re-crack
ing said second naphtha fraction in the presence
of between about 5% and 30% Vby volume of a
light feed consisting essentially of at least one
hydrocarbon having from 3 to 5 carbon atoms per
in the range of about 90° C. and 230° C., non-cata
lytically re-cracking said second naphtha frac
tion, separating the resulting re-cracked prod
uct by itself to produce a third naphtha fraction
boiling essentially within the range of about 100°
C. and 200° C., treating said third naphtha frac
tion to remove a major portion of oleñns therein,
further separating said third fraction by itself
into a light aviation' base stock boiling essentially
within the range of about 100° C. and 150° C.,
and a heavy fraction boiling essentially within
the range of about 150° C. and 200° C., further
molecule, separating the resulting re-cracked
product by itself to produce a third naphtha frac
tion boiling essentially within the range of about
100° C. and 200° C., treating said third naphtha
y fraction to remove a major portion of the oleñns
therein, furtherfseparating said treated third
naphtha fraction by itself into alight aviation '
base stock boiling essentially Within the range of
about 100° C. and 150° C., and a heavy fraction
boiling essentially within the range of about~150°
C. and 200° C., further non-catalytically cracking
non-catalytically cracking said heavy fraction,
separating the resulting further cracked prod
uct by itself to produce a heavy aviation base
stock boiling essentially within the range of about
100° C. and 200° C., each of said cracking oper
ations being conducted at a temperature between
said heavy fraction in the presence of between
about 5% and 30% by volume of a light feed con
sisting essentially of at least one'light hydrocar
bon having from 3 to 5 carbon atoms per molecule,l
about 540° C. and 580° C. and at a pressure be
tween about 40 and 100 kg./sq. cm.
separating the resulting further cracked product
'
by itself to produce a heavy aviation base stock
boiling essentially Within the vrange of about 120°
C. and 190° C., treating said heavy aviation base
stock to remove a major portion of the oleñns
by volume of concentrated sulfuric acid and re
therein and blending the resulting treated heavy
distilling the acid treated fraction to remove any
aviation base stock to produce an aviation fuel,
polymers formed by the acid. .
12. The process of claim 10, wherein said heavy 35 each of said cracking operations being conducted
at a temperature between about 540° C. and 580°
aviation base stock has a boiling range between '
C. and at a pressure between about 40 and 100
about 120 and 180° C.
kg./sq, cm. y
»
13. The process of claim 10, wherein said heavy
IVOR G. NIXON.
aviation base stock is also treated to remove a
11. The process of claim 10, wherein the said
treating step comprises contacting said third
naphtha fraction with between about 1% and 5%
30
major portion of oleñns therein.
40
'
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