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. 17; 1946.
Filed Oct. 14, 1943
Patented Dec. 17, 1946
John C. Monday, Cranford,-N. J., assigner to
Standard Oil Development Company, a corpo
ration oi' Delaware
Application October 14, 1943, Serial No. 506,169
1 Claim. (Cl. 20o-683.4)
This invention relates to the production of
aviation gasoline.
In the catalytic cracking of hydrocarbon oils,
naphthas are produced which have a relatively
high octane number, but as ordinarily produced,
they are not of high enough quality for aviation
gasoline. Various methods have been suggested
for treating catalytically cracked gasoline or
v naphtha to produce aviation gasoline. My pres
der to maintaincatalyst activity. The. yield of
aviation alkylate was 125% of the 60-150° F.
fraction and the A. S. T. M. octane number was '
87.5. The aviation octane number-|-4 cc. llead
per gallon was equivalent to iso-octane+0.24_ cc.
lead per gallon.
Example 1A
A 60-200° F. fraction from the same gasoline
ent invention is an improvement over such other 10 containing 8.8% aromatics when alkylated under
the same conditions required an acid replace
ment rate of Y1.5-1.8 pounds per gallon of al
According to my invention, a relatively heavy
kylate in order to maintain activity. The yield
hydrocarbon, such as gas oil, is cracked in the
of alkylate was 118% and` thel A. S. T. M. octane
presence'of a catalyst at a relatively high tem
number was 85.
perature and from the cracked products are sep
arated a light naphtha fraction, a heavy naphtha
fraction, and a heavier oil'fraction.
The light
naphtha fraction is alkylated with isobutane, and
Example 1B
If a 400° F. end point naphtha is subjected to
alkylation. the yield is very low and the octane
'the heavy naphtha fraction is 'subjected to 'a
number of the product may actually be lower
catalytic recracking operation. The products 20 than that of the `feed stock as a result of the
from these steps are then fractionated to sepa
rate light hydrocarbon fractions boiling in the
~ absorption of aromatics by the catalyst and the
alkylation of aromatics thus forming compounds
boiling above the gasoline range.
In the alkylation step, the oleiins react With
of high stability, high octane number, high sus 25 isobutane to form saturated hydrocarbons of
ceptibility to tetraethyl lead and high rich mix
high clear octane number, high octane number
ture performance. Furthermore, the ethylene
appreciation on the addition of tetraethyl lead,and butylenes produced in the cracking and re
high blending octane number, and high per
cracking steps may also. be subjected to alkyla
formance when employing rich fuel/air ratios
aviation gasoline range, and the fractions are
blended to produce a finished aviation gasoline
tion with isobutane since the product alkylate is 30 as in take-oil or under heavy loads as measured
of high quality and augments the yield of avia
by the AFD-3C test method. Each of these fac
tion gasoline.
tors is of prime importance in the production
The light fraction of the catalytically cracked
of large quantities of aviation gasoline having
naphtha which is fed to the alkylation step
octane numbers of 100 or above. Removal or
should be substantially free of aromatics. The 35 conversion of the ole?lns in the naphtha is nec
end p-oint should be chosen to exclude benzene,
essary to achieve this end, and the alkylation ofl
if an appreciable amount is formed in the crack
the light catalytic naphtha originally contain
ing step. For example, the end point may be
ing about 40% oleñns lowers the bromine num
165 or 170° F. In some cases wherein the amount
ber from about 82 ogs/gm. to less than l.
of benzene is very small the end point may be
In the catalytic recracking step, also, oleñns
200° or somewhat higher, but it should be borne
are converted. so that the blend of alkylated
in mind that the presence of even small amounts
of aromatics in the alkylation feed stock re
sults in rapid degradation of alkylation cata
‘ lysts, as well as in lower yields and lower oc
. tane number products. This will be evident from
the following Examples 1, 1A and 1B, Example
1 showin-g my preferred alkylation step and EX
amples 1A and 1B showing poorer results when
selecting improper fractions.
Example 1
A Sil-150° F. fraction containing no aromatics
from catalytically cracked gasoline was alkylat
light naphtha and èatalytically r'ecracked heavy
naphtha has a low bromine number and low acid
heat and easily passes speciñcations. Since in
the recracking of the heavy naphtha lower boil
ingoleñns are produced, in a preferred modiii
cation of my process the light naphtha pro
duced in the recracking step is passed‘to the al
kylation unit along with the light naphtha pro
50 duced in the catalytic cracking. In this manner
there is produced an aviation gasoline of quite
low oleñn content and very high quality.
Apparently the oleiin content is reduced in the
catalytic recracking step partly by polymeriza
ed With isobutane at 45° F. employing a 10/1 55 tion and partly by hydrogenation through hydro
isobutane/olefin ratio andI sulfuric acid catalyst
in 'a 1/1 acid/hydrocarbonV ratio for 30 minutes
gen exchange with naphthene hydrocarbons.
The recracking causes a sharp reduction in the
.amounts of naphthenes and parañlns present,
contact time in a continuous run of 103 hours
particularly in the high boiling portions which
duration. An acid replacement Arate of 0.5 to 0.7
pound per gallon of alkylate'was required in or 60 are very high in aromatic content.
and this- base stock has an aviation octane
number-+4 cc. lead of 98.2. Blending of the
The heavy fractionof the catalytically cracked
naphtha which is subjected to catalytic recrack
alkylate and recracked aviation base stock gives
ing must likewise be a selected fraction if high '
a yield oi _83% of aviation gasoline based on the
410° F. end point catalytic gasoline in addition
to the pentane produced in recracking, and the
aviation gasoline+4 cc'. lead per gallon has an
aviation octane number of 100 and a rich mix
ture performance ' equivalent to about iso
yields of high octane number aviation gasoline
are to be realized, as shown by the following ex
amples. Example 2C shows improved yields ob
tained when catalytically recracking a selected _
heavy naphtha fraction, _whereas Examples 2,12A
and 2B show that best results are not obtained
10 octane+1.8 cc. lead per gallon by the AFD-3C
with improperly selected fractions.
Example 2
As pointed out'above, the yield and quality ofthe aviation gasoline maybe augmentedÍ by
A 'l0-410° F. naphtha produced by catalytic
temperature lin , the
alkylation of the ethylene and butylenes produced
by cracking and recracking with the isobutane
925-975° F. with powdered synthetic silica
produced by cracking and recracking. In view
of the requirements of norm‘al butene and iso
alumina gel was recracked at 900° F. with the
same catalyst and the product was fractionated.
butylene as feedstocks 4in synthetic rubber pro
duction, it may be desirable vto`-`alkylate only the '
The yield of 335° F. end point aviation base stock.
exclusive of pentane was 46.8% and the yield of
ethylene at the present time.V The ethylene
pentane was 25.9%. The aviation octane num 20 should be alkylated with isobutane in a separate `
ber+4 cc. tetraethyl lead per gallon of the feed.
unit not in the presence of sulfuric. acid catalyst
stock to recracking was 88.7 while that of the
but in the presence ofïa halide catalyst, such
depentanized aviation base product was 94.2.
as aluminum chloride or bromide, employing
Example 2A
about 3/1v to. 5/1 isobutane-ethylene ratio at
A 11o-220? F. fraction of the same gasoline as
25 100-150° F. and 250-350 lbs./sq. in. pressure.
The product contains 'I0-85% of Ce hydrocarbons,
predominantly v2,3-dimethyl butane'which has a
employed in Example 2 was recracked under the
same' conditions. The yield of aviation gasoline
very high rich mixturerating on the AFD-3C y
base exclusive of pentane was 58% and the yield
of pentane was 14%, while aviation octane 30
The ethylene alkylate, or only the Cs fraction
numbers+4 cc. lead of the >feedand ofthe de
therefrom, is blended with the aviation fractions
produced by alkylation of the light catalytic
naphtha and by recracking the'heavy fraction
of thecatalytic naphtha. When operating sol as
pentanized aviation base product were‘86.4 and
y 92.6, respectively.
V A' Example 2B i a' _, '
A 11G-289° F. fraction of the same gasolineas'
to alkylate ethylene and C4l oleiins as well as _
theïlight catalytic naphtha, the yield of finished
high quality aviation gasoline'is more than 100%
based on' the original catalytic naphtha.
employed in Example 2 was recrackedunder-the
same conditions, . and. yields `of 61% vof dac-'.
pentanized aviation' base and 11.3%_of 'pentane
were obtained. The feed had‘an aviation octane '40 In contrast to ethylene alkylation, either the
Vnormal butenes or -isobutylene or both can be
number-F4 cc. lead of 88, while that of the de
alkylated with isobutane in-‘the presence of sul
pentanizeal aviation b_ase product was 92.5.
furic acidcatalyst with good results, and it is
Example Í2C '
preferred 'to do thisȢsimultaneously and in the
A 220-410° F. fraction4 of the gasoline employed f45 same unit as employed in the alkylation of the -
in Example 2 was recracke'd'under the >same con
light naphtha fractions.
In the drawing, the figure represents one form
ditions. ’ The feed' stock .contained 38.2% ,of
material boiling in the .aviation gasoline range ¿ of apparatus which may be used to practice my
below» 3_35" F. The yield ci depentanized’aviation
base was 5,8%; the pentaneyield being 4.4%, and
vReferring now to the drawing, the reference
the yield of C4 hydrocarbons being 5.5%. Where 50 character'lll designates aline _through which the
as .the aviation octane .number-’r4 cc. leadof the
hydrocarbon oilfeed stock is introduced to the
feedstock was 87, that lof the depentanized avia
system. For example, the feed` may comprise
gas .oil vapors4 or votherrelativelyheavy vapor- v
It base
has product
Abeen found‘that
was' 98.2.' ~ _` ,the fraction«of~
catalytically _ cracked gasoline boilingï- between
about 160° or 170°v F. and-"about 220° F. has va
low 'octane number,
for»y example, ` about- 84 -
aviation+4 cc. lead, and that» recracking im
»ized petroleum stock.v When4 using powdered
catalyst, it is also possible to startv with> a partly 1
preheated liquid stock andto supply the heat of
vaporization and conversion by contact with a
suilicient quantity of hot catalyst. The hydro
proves ‘it lonly slightly, for example,-to about _88.
carbons> are cracked at atmospheric pressure or
It is generally preferred >to discard this'fraction, 60 thereab'outs at'a temperature of about 900° F. to ,
which may amount to 10 or 12% of the catalytic
1000°. F., preferably about-975° F. when cracking
gasoline, and to use it in automotive fuels. When 'a
a relatively heavy gas oil having an A. P. I. ~
discarding this fraction the charge'to the alkyla
gravityof 25430"v and a mid-boiling point of
tion unit is about.48% of the catalytic gasoline -
exclusive >of C4 hydrocarbons, and the 220-410° F. 65
fraction charged to the recracking step amounts
to about 40% of the catalytic gasoline.
As shown in VExample 1, the yield Vfrom alkyla
` about 60G-750° F.
Thecatalyst may be 'any suitable cracking
catalyst, such as synthetic silica alumina gel, syn
thetic silica magnesia- gel, acid-treated bentonites,
etc. For the preparation of aviation gasoline
tion is 125%.of the charge„or 60% based on- the
catalytic gasoline, and this alkylate has an avia 70 and relatively large amounts of oleiins, it is pre
ferred to use the synthetic silica alumina gel.
tion octane number-i4 cc. lead greaterthan 100
The preparation of such a catalyst is well known
(iso-octane+0.24 cc. lead) . As shown in Ex
and is ,not described here.l Instead of vusing
ample 2C, the yield of depentanized aviation base
catalyst, it is within the contempla
stock from the recracking step -is 58% of the
invention> to use larger particles of
charge, or 23% based on the` catalytic gasoline. 75
_amaca ’
catalyst in a moving bed or to use larger particles
tower 32 through line-38 and are subjected _to l '
catalyst has a size o_f about 200 to 400 standard
arate fractions rich in ethylene and in C4 hydro
carbons. These operations, which are well known
'in iixed bed operation.- Preferably the .powdered ' ‘ fractionating and/or scrubbing operations to sep
mesh or finer.
The hydrocarbon feed stock is passed through
» line I0 into the bottom portion of a reaction
vessel I8 which contains dry powdered catalyst
and need not be described in detail here, are in
- dicated on thedrawing by numeral 43. Light
' gases pass overhead through line 44. A C3 frac
at reaction temperature. The velocity of the î tion is withdrawn through line 45. -The sep
4arated C4 fraction withdrawn through' line 45
vapors passing throughreaction vessel I8 is con
trolled so that the catalyst -particles remain in 10 contains isobutylen‘e which is useful in the pro- ‘
duction of synthetic'rubber and the isobutylene
the vessel for a much longer period of time than
may be recovered by scrubbing with acid. The
the vapors, and preferably such that a relatively
acid used is preferably sulfuric acid having a
densev layer of catalyst is present in the lowerconcentration of about „65% by weight. The C4>
portion ofthe vessel. - Suitable velocities lie in_
the range from 0.5 to 10, preferablyvl to 3, linear 15 fraction is introduced into the bottom portion
feet per'second when employing 200-400 mesh
catalyst having a density when freely settled of
of an acid scrubbing vessel 48, the acid is intro
relatively dense catalyst phase is aerated by the
from the`acid by treating with steam, thus rais
ing the temperature to about 250° F. and lowering
the acid concentration to Ll0-45%. Isobutylene
duced at the top through line 52, and the acid
extract is removed through line 53. In the scrub
from 35 to 60 lbs/cu. ft.' Under these condi
bing vessel 48 the temperature of the sulfuric
tions the relatively dense catalyst phase has a
density of the order of 10 to 30 lbs./cu. ft. The 20 acid is about 75° F. The isobutylene is recovered
rising vapors and has the appearance of a violent
ly boiling liquid, and possesses properties of
and di-isobutylene are ñashed overhead and the
static pressure and a level or meniscusY which is 25 latter is cracked to form isobutylene. If iso
liquids such as fluidity, the ability to exert hydro
butylene is not desired for synthetic rubber, the
especially noticeable when low vapor velocities
entire C4 cut is by-passed around acidv scrubber
are employed. Also, when employing relatively
48 through line 54 to line 56 leading to alkylation
low velocities, such as from 0.5 to 2 ft. per second,
unit 51.
the carry-over of catalyst by the cracked prod
uots is very small, of the order of 0.003-0.01 30 , 'I'he rest _of the C4 fraction containing isobutane
and butenes leaves scrubber 48 through the line
lbs/cu. ft. of vapors.
55 and is mixed with a light naphtha fraction
The cracked products leave the top of the re
introduced through line 58. This light naphtha
action vessel I8 through line 22, after lpassing
fraction is withdrawn from the upper part of
- through cyclone separator 24 where entrained
powdered catalyst is separated therefrom. » Cy 35 fractionating tower 32 wherein the catalytically
clone separator 24 is preferably located inside
cracked products ~are fractionated. The light
naphtha fraction collects on trap-out tray- 62 in
the fractionating tower 32 and is passed through
separating means may be used. Separated
line 58 by pump 64. The light naphtha fraction
catalyst is returned to the reaction zone proper
through linie 25. During the conversion oper 40 contains oleñns and para?lins, but as mentioned
above, should be substantially free of aromatics.
ation the powdered catalyst becomes contami
The light naphtha fraction has a boiling range
nated with coke or carbonaceous material and
of about 60° to about 170° F. or 200° F.
lt is necessary to regenerate the catalyst in any
The mixture of the light cracked naphtha and
known manner,l preferably by burning with air
or oxygen-containing gas at about 1000--1l00"l F. 45 the C4 fraction is passed through line 58 to the
alkylation unit or reactor 51 wherein the oleñns
toV remove the carbonaceous deposit. Catalyst
are alkylated with isobutane to transform the
for regeneration is withdrawn from reaction
the upper portion of vessel I8.
Other forms of »
vessel I8 through line 26 in a ?luidized condition
and is passed to a regenerator (not shown)
Ywhich may be similar in construction to vessel
i8. Hot regenerated-catalyst is returned to line
I0 and to the reactor through line 28 at a suiii
olefins to branched parafñns. Any suitable al
kylation -catalyst is used, such as sulfuric acid,
boron fluoride-water, hydrogen fluoride, etc.
Where sulfuric acid is used, the titratable acidity
of the acid is maintained above about 82%, pref
cient rate to maintain reactor` temperature and ‘ erably at about 85~90%, by continuous .replace
ment with 94-98% acid. The temperature dur
catalyst activity at the desired levels, vand if
liquid feed stock is being supplied to the re 55 ing alkylation is preferably in the range li5-`-80"`
action, to absorb or vaporize the liquid corn
pletely. The weight ratio of catalyst to oil. em
F. The ratio of isobutane to oleflns in the feed
‘ is generally maintained at 3/1ior higher by re
cycling isobutane separated from the products,
and the vinstantaneous isoparaiiin/oleñn ratio in
While I have shown only one cyclone separator 60 the reactor is maintained considerably higher, for
ployed is generally above 3, for example, from
5 to 20.
on the drawing, it is to be understood that more
than one cyclone separator may be used in series
example, 30/1 or 100/1 or'greater, by recycling, .
products which are low in oleñns to the inlet of
to effect a better separation of powdered catalyst I
the reactor.
The acid for the alkylation unit is introduced
from the vaporous reaction products. The sep
arated vaporous reaction products pass overhead 65 through line 'l2 and spent acid sludge is with
drawn through line 'M_ The products of alkyla
from the separating means 24 through line 22
tion are passed through line 76 into a second
and are passed to a fractionating tower 32 for
fractionating tower ‘I8 for separating the desired
separating desired fractions from the cracked
light hydrocarbons boiling in the aviation gaso
products. Condensate oil is removed from the
bottom of the fractionating tower' 32» through 70 line range from higher boiling constituents. The _
light hydrocarbon constituents lpass overhead
line 34 and may be recycled to the reaction. zone
through line 82, are partially condensed in con
I8 or withdrawn from the system.
denser 84, and passed to a separator 86 wherein
The light uncondensed constituents comprising
gases are separated from liquid. The gases com
hydrogen,v methane, ethane, ethylene, C3 and C4
Vhydrocarbons leave the top of the fractionating 75 prising C4 and lighter pass overhead through line
' 'Í r
boiling above the aviation gasoline range reduces '
I8 ~and are fractionated in equipment (not shown)
_their boiling points and thereby increases the
yield of aviation naphtha.
The'vaporous reaction products pass overhead
to -separate isobutane'which is recycled to the
alkylatio'n. unit 51. The light aviation naphtha
‘ fraction is withdrawn froml separator 86 as a liquid
from reactor ||0 through line |24 to a third
through line 82. This light fraction boils up to
the end point of the desired aviation gasoline,
fractionatingtower |34. During the recracking.
of the heavy naphtha fraction additional amounts
generally 30D-330° F. and is substantially free of
oleñns. Higher boiling constituents are.¿withdrawn from the bottom of the fractionator 18
. of isobutane are formed together with other val
uable light oleñnic hydrocarbons. These light
hydrocarbons are withdrawn from the top of the
through line 94. These higher boiling constitu
ents may be addedtogordinary motor gasoline.
As mentioned earlier, it is >frequently _desirable
to alkylate the ethylene produced in the cracking
fractionating tower |34 through line |36 and are
.combined withthe gaseous products leaving the
ñrst fractionator 32 through line 36. This mix
ture is then treated to separate isobutane and
olefins from the other gases vfor use in the alkyla
and recracking operations with isobutane. To
this end the ethylene separated in fractionating
and scrubbing equipment 43 and which may have
a purity from`25 to 80% is passed through line
85 to an alkylation unit 86 where it isalkylated
with isohutanel in the presence of aluminum ch1o-'
ride. Isobutane is introduced through line 91.
tion units 51 and 86. ,
'_I‘he reaction products in the iractionator |34
`.The isobutane may come from cracked >products
are fractionated to separate an aviation naphtha
fraction vwhich collects on trap-out tray |40.
This‘fraction is relatively heavy, boiling for ,the
most__'part-between about 190 and 335° F. and
v in my process or froman extraneous source. The
- conditions of operation are similar to those em
gasoline._ The aromatic content of the naphtha
contains high quality constituents for aviation
ployed in alkylation unit ä‘lexcept that the tem- . is very high, lparticularly of the 22o-335° F. frac
perature- is higher (1D0-150° F.)‘.and»the pressureV 25 tion -which mayfbe v80-90% aromatics or higher.
may be 250K-350 'lha/sq. in.1The `products are ' The naphtha fraction is withdrawn from trap
_ passed through'1ine’98`into fractionatorJB along :out‘tray |40through line |42 and is mixed with
the, »light .alkylate fraction withdrawn through
with the products from 'alkylationunit v51.
linef92 and the -mixture is Withdrawn through line
tionating tower 32, the catalytically crackedprod 30 V| 44 _as 'an aviation gasoline.y The addition of 4
Returning now to the first-mentionedl frac
or 4.5`cc.~`_of- tetraethyl lead per gallon andad
ucts are further fractionated to separate aheavyf _
naphtha fraction which is .withdrawnv from trap
` justment of 'the vapor pressure by adjustment of
‘out tray |02 through line |04 by pump |06.- _ '_I‘his
1the’isopentane content of the gasoline produces
_heavy naphtha fraction has'an initial' _boiling ' -a finished aviation gasoline of high stability and
~ point from about 170° F. to about 4220" F. and may 35 high octane_numberby both the aviation octane
have an end point of 350 or -400 lor somewhat
number 'and the AFD-3C methods of testing.
higher, and contains oleñns, parafilns, aromatics
._A heavier `fraction collects on lower trap-out
andnaphthenes. vThe paraflinsand some of the
tray |46'in.th_e fractionating tower |34 and this
ality for aviation vgasoline
are ofr poor
fraction is withdrawn through line |48. This
and it is> desirable-to'convert them to‘higher
heavier fraction may be added to motor gasoline.
quality constituents for aviation gasoline. à Also
In a preferred modiñcation, a light fraction of
Isome of the alkylated aromatics‘have a high boil-l ' ß 'the recrackedproducts, and which contains ole
ing point and. it i_s desirable to _break oft'part of
the chains of the alkylated aromatics to reduce
their boiling point.
trapfout Atray |50 and is passed through lines |52
and f_58 toalkylation .unit 51» with isobutane' along
To improve the quality ofthe heavynaphtha u with the light'ïcracked naphtha of similar boiling
range'.~_ In _this 'case only the recracked heavy
cracking operation in reactorl'llß. The‘recrack
naphtha' fraction is passed directly through line
ing unit is` operated in the same manner as the
|42¿forgbl_ending'with the alkylated naphtha.
fraction, it is passed- through a second catalytic ,
- cracking unit described earlier, employing vpow.-v
.While _I _have shown one form o_f apparatus and
dered cracking catalystof thesame or different
have'given conditions for carrying out the differ
ent steps' lin-niy process, it is to be understood
that theseare by _way of example and'changes
and modifications may be 'made without depart-‘
_ composition.' Synthetic silica-alumina gel is a`
preferred catalyst. The temperature -of opera
tion is generally slightly lower than in cracking,
V "for example, '700'tof950° F., particularly if the
ing' from'the spirit of my invention.
cracking unit is `operated toÀ give -high conver
II claim: ‘ " ‘
sions. With cracking conversions of the order
` . ¿A methodbt 'producing aviation 'gasoline which
of 60-80%, 900° F. is a suitable temperature for
comprises. ¿separating a catalytically Acracked
1 _ recracln‘ng. A stream _of catalyst is continuously- . '_
fraction having a
-Withdrawn from the reactor through line |'|2, re ‘ Í boiling frange o_f_lightlnaphtha
about Gti-165° F., an interme
generated and _returned through line _| I4. . A cy-i
‘ diate naphthafraction having a boiling range ot
. clone separator H6 and return pipe |'l8 ‘are- used.~`
about ITG-'220° F.,'and a heavy naphtha fraction
_ A common regeneratoris preferably employed for '
regenerating catalyst'from the` cracking and re
cracking operations.
_ - During the second cracking‘step paraffins, Lole
ñns and naphthenes are cracked, isomerized` and
dehydrogenated into isoparañins and aromatics
and at least some of the olefìns are removed and
‘ having a boiling range of about 22o-410° F., a1
kylating- the separated light naphtha fraction
` with isobutane to transform oleñns to branched
chain hydrocarbons.' discarding the separated in- '
termediate naphtha fraction, catalytically crack
ing theheavy naphtha 4fraction to higher avia
others are reformedv into higher quality vconstit 70 tion qualityl constituents and combining said al
uents for aviation gasoline. `The aromatic con-V
stituents originally in the heavy naphtha fraction
` passing to the reaction zone ||0 remain as aro
matics, but de-alkylation of alkylated aromatics
kylated products Withsaid catalytically cracked
heavy'naphtha fraction to produce. aviation gas
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