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Патент USA US2403714

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July 9, 1946.
l
F. E. FREY
PRocEss FOR THE `'JJREATNIEM' 4011'.l-I'unmocARßoNs
Filed July 11, 1942
NN
2,403,714
Patented July 9, 1,946
. uNflsTEofl-STATES PATENT:
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2,403,714-
j
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PROCESS FOR'rHE Tit’lgnjlïl’yiENT'oir'-Y Y
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`HYDROCAR-BONSy
I
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Frederick E. Frey,Bartlesville;l Ókla.; assigner-ato:l »
Phillips VPetroleum Company, a= corporation of»,
3
l ,Y §- K
Delaware'
Applieationculy 11, l1942-,"l varial No; «teaser _'
Y 1a claims.vv (ol. ¿Q01-_1683.49
alkyiating,?elativelylmwáf Y
4process for
This' invention relates' ,tothe treatment; Of by: ` ca‘ftio'nf> inla
alkylatableY hydrocarbons in tlfieï'presenceÈ
drocarbon»materials.l More particularly’ it V,ree ' *boiling>
of ñuorin'e‘. compounds;` ‘a selected'ipartl or`r all bof'
lates-:to the conversion, vley-'an alkylation reaction '
‘ the hydrocarbon. effluent from ranïalky'latin'g 'zone
may: be f advantageously ysubjected toïthegaction
in the presence of a iiuorine-containing catalyst,
of> relatively lowl-vboilingvv Yhydrocarbons to motor
of. a s'olid porous- c‘ontact: material `toirern’ove‘.o'rV->>
fuel hydrocarbons.` _Still morefparticularly, it re- '
lates to the removal of organically combined fluo
lrine from the product vof such'fconversion. This`
application is ’acontinuation-in-part of my` co
pendingapplication,,Serial No. 398,361A,vñled June
»ganic‘ ?luorine'coinpounds‘.
pounds. asvr impurities.`
16,.1941, now U. S. Patent 2,3‘l7,945,issued May
2,1944-i
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Y An'lobject'of this invention isito efîect’substan- '
tiallyfcomplete removal of .'ñuorine; fromuhydro-f 10 carbon~ >liuids' containing organic ‘fluorine ` .come
,
Al further: :object :of ¿this-ï invention is ank »imi
,
l proved'lpr'ocesssfor’obtaining. a substantially fluo-->>
y In'the manufacture; of rhydrocarbons by proc
rime-free A»a'lkylate ëfrom" the' alkylationi of hydro#
esses in which»Viiuorine-containinglcatalysts are
15 Vcarbons .in the >presence-tof al catalyst ’_coxm'irlsingV - Y
,y a iluori'ne compound.
taining byfproducts‘are formed.V t These vprocesses
used, small proportions of organic'fluorine-.con
`other objentsfand advantagfsfwiu .begabnarent -
may involve reactionsisuch aspolymerízation and
fromy ythe ‘followingfdescrìptionçitne accompanying
alkylation of relatively low-boilinghydrocarbons
drawing, andî/o'rfthe appendedaclaimse». » .Y »
to produce motor-fuelhydrocarbonsin the pres
encerof catalysts lcomprising one or more of such 20
iluorinacompoundsI asf¿h'ydrofluoric acid, boronY
trifluoride, and the like.
AIn ¿accordance with' »the A‘present .inventio'rrgf‘fl
have now found that the undesirable organic Vflu-f
orinœcompounds ¿differ among". themselves-with
respect >~to .the ease‘withlwhi'ch the lorganic' »ñuo‘nv
Although the exactna-r ,
ture or composition of. the organic fluorine-con
rine can'be removed. » For example, when th‘eltoe
taining by-¿products which _may bekvformed has
tal- hydrocarbon eiliuenti ,fromj a- hydroñuoric. acid
alkylation process ris treated to remove iiuorin’e,~
as by\.contacting Withbauxite, and subsequently
not been deñnítely establishedythey are believed
tobepredominantly alkyl and/tor aryl. fluorides.
They are not .completely removed by vwashing the
hydrocarbons -with alkali solutions, They tend
to ‘decompose Yat ‘eleva'taiV temperatures; 'suon as
those employed in fractional distilïaticncf' the' -
is .separated intoffracti'ons of. different boilingv
ranges; the residual organic iluorine, whichfhas
not been'-4 removed. byi the defluorinating treat*l
Which‘is corrosive",Y especially :in the Y‘presenceof
Y ingvi‘ractions;y ,Althoughëiti is possible bythe
ment, is concentrated in therlrelatively>higl'reboilè»
hydrocarbons, rtherebyj'forming"hydrofluoric acid,
ì
n moisture. "
process of the-aforementioned c'open‘ding applica>-~`
'Inggases theyima'y thus'fcause'corro- Y
tion to remove substantiallyî'all'lfluorine in asin#
gle treatment by- .fusing suili'cìentlydrastic oper-.
sion‘of handling‘equipment; inliquid motorffuel '
hydrocarbons‘they“ areV undesirable forreasons l.
thatlare obvious.` 'f
Y
.
_
ating conditions;~.I have found it is 4advantageous
~ to` treat; the xalkylationeiiluent under such .condif A
According toy the* aforementioned“ co-pendin'g
tions thatrtheïloiv-boilingxorganic fluorine'. is' re-r`
application,V organic ñuorine compounds'may ' be
removedv 'from hydrocarbonmaterials containing
them by 'contacting' such hydrocarbonniaterials
40
withj solid porous Contactk materials. Contact~
materials which have been found-suitableginclude
moved, then to‘sep'arate from the eíiluent at leastv
one; relatively ¿high-¿boiling fraction'yand- ñnally .to
treat this relatively high-_boiling fraction tome-f
rnove'the high-boiling:organic-fluorine.
Thereby '
the .most advantageousconditions for the removalof each type of organic ñuorinezcan .be usedr-andV
genatíon or dehydrogenationreactions, such as
alumina gel, activated aluminagidehydrated baux 45 equipment of' a givenA size or> capacity can'be- uti-'
those vknown to. be catalyti‘cally active for hydro- , n
ite, chromium oxide,r‘rnixturesy ofi~ alumina»` and
chromium. oXide,ïmetals-"of the iron group,»-»es-peci'ally ñnely divided` nickel deposited onr an'- in@
” lizedto the fullestadvantage.:
» Y Understandingcofamyinvention maybe aided y
c >by reference ltothe;accompany-ingdrawing; whichA
erh-support, andïtlielikegl Such'contact mate- ' isf a schematic ilowediagram Yof one arrangementl
of apparatus-for practicingthe inventionl;
rialsfappear to adsorb preferentially the organic>
fluorine- compounds;y althoughthe exact mecha-
Y
agent,A for example >an -.isoparafûn ' such as isobu-=
ni‘smilnvolved is’ not ful-ly known.atapi'esegui'.Y.n . The
` tane or isopentanerandian oleñn’such as propyl'
hydrocarbon material: being 'treated'.may. be. in".
eitherfthe liquid ort'the.:vapor1ïphase.‘ Also,. ac-,_
cordin’g‘rto the~ aforementionedcof-pending appli-1`
- Y
»Analkylatable hydrocarbon and an'alkylating
f ene or one orgmorejlof; the butylenes, respectively,`
55
Vai:efadmitted-preferably«through a number of _in
2,403,714
3
lets, such as that represented by inlet I0, and/or
through conduit II and pump I2 to alkylator I3,
in which' they are agitated under alkylating con
ditions with concentrated or substantially anhy
drous hydrofluoric acid, which may be admitted
through inlet I4 and/or conduit I5 and pump I6.
In the feeds to alkylator I3 the mol ratio of iso
parañin‘to olefin, or other alkylating agent, such
as the corresponding alcohol or halide or the like,
masses which have been found suitable are
alumina gel, activated alumina, dehydrated
bauxite, chromium oxide, mixtures of alumina
and chromium oxide, metals of the iron group,
especially finely divided nickel deposited on an
inert support, floridin, diatomaceous earth, and
the like. Such contact lmaterials appear to adsorb
preferentially the organic iluorine compounds,
although the exact mechanism involved is not
preferably having three to five carbon atoms in 10 fully known, The hydrocarbon material being
the alkyl group, is preferably in the range of 2:,1
treated may be in either the liquid or the vapor
to 20:1 or more, and the Weight ratio of hydroñu
phase; -since the volume is relatively small in the
oric acid to total hydrocarbons is preferably in
liquid phase condition, and since all the mate
the range of about 0.211 toj`4:1.-v_ The’ feed, or at
rialsinvolved in this process are easily maintained
least the portion of the feed which 'contains the 15 in the liquid V_state under the preferred operating
alkylating agent, is preferably introduced into
conditions, it is preferably treated in the liquid
th'e reaction mixture under conditionsfof’high
state. In general, theconditions of temperature
turbulence and/or in multipointwise fashion, so
and contact time in dei‘luorinator 28 should be
that the alkylating agent is rapidly mixed 'and
reacted with the isobutane or other alkylatable
hydrocarbon'.~ Thisv procedure is advantageous. in
Well below those which would induce deteriora
tion or alteration of the hydrocarbon material.
Temperatures‘between about 50 and 4:00"` F. may
orderto: favor the. desired .olefin-‘isoparaflin j unc
be employed. ’ The optimum temperature ’in any
tures, or» alkylation reactions, and to hinder un
particular instance Will depend upon the nature
desirable olefin-olefin junctures,. or polymeriza
of the contact mass, the nature of the material
tion reactions. Preferred'operating conditions in 25 being treated, and the desired degree of removal
alkylator I3,v as vfor example `for alkylating iso
of fluorine. The `preferred temperature, particubutane with’ butylenes, to which for the sake of
larly when bauxite is used, is approximately
`simplicity this description maybe primarily de
voted, 'are a temperature in >therange of 30°> to
equal to or somewhat‘lower than the kettle tem
perature of column 2 I , and is usually in the range
l5.0°-.F., a pressure suiñcient to maintain all com 30 of about 150 to 350° F. By using such a tempera
ponents in the liquid phase, and a contact‘time
ture, the necessity for heating or cooling in de
or time of residence in the alkylator. of about l
ñuorinator 28 is avoided, and the removal of
to 30 or more minutes; however, conditions out
iluorine, especially offthat fluorine which upon
sidelof> these ranges may be used Without passing
distillation of the vfluorine~containing material
beyondthe scope of this invention. _The opti 35 appears in the low-'boiling distillate fractions,
mum alkylating conditions _vary with different
such as 'the isobutane and butano fractions, is
reactants;v 'for example,fin alkylating benzene
with ethylene, or‘normal butane with oleñns, in
sufhciently complete that corrosion of equipment
by fiuorine compounds in the hydrocarbon mate
the presence.` of .hydroiluoric acid as a catalyst,
the-preferred Vtemperature is in the :range of 200° 40 rial is substantially Completely eliminated. While
the same type of contact material may be utilized
to 350° F. ~ =
~
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.
vAfter a suitable contact or reaction time, the
resulting mixture passes through conduit I'I to
separator I8, wherein >it is separated into two
liquid phases, as by cooling and/or gravitational
or.`centrifugal means.
The heavier or hydroä
fluoric acid. phase preferably is recycled', as
through conduit I5, to alkylator I3; part of it may
Abe withdrawn, as through valved outlet I9, and
passed topurification or acid-recovery steps, not 50
in both steps, different »materials of the class de
scribed may be usedin each-defluorinating step.
At relatively high temperatures, Yvery high
space velocities, such as about 2000 or 3000 vol
umes of vapor (or an equivalent number `of vol
umes of liquidrper volume of contact material
.per hour, are'satisfactory; at relatively low tem
peratures, the space velocity should be compara
tively low, such as perhaps 1 or 2 volumes of liquid
per' hour. In general the optimum space velocity
depends not only upon the temperature but also
Y The lighter. or hydrocarbon phase is passed
upon such factors as the content >of fluorine, the
through conduit 20.to azeotrope column 2|, in
pressure used, the desired extent of iluorine re
which it is'v separated vby fractional distillation
into two fractions.. vThe overhead fractioncon 55 moval, and the particular Acontact material in
use'. A suitable space velocity >for any particular
sists of an 'azeotropiemixture .of hydrogen fluo
application may be readily found by trial by one
rideY and low-boiling paraffin hydrocarbons, such
shownin the
drawing.
as ¿propane and isobutane.
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.
This fraction is
passed throughconduit 22, condenser 23, and
conduit 24. tosep-arator 25, wherein it is separated
into 'two- liquid rphases, as by> cooling and/or
vgravitational or. centrifugal means. . All of the
lighter. or hydrocarbon phase is returned through
éondu'itZGvas vreflux to azeotrope column 2l;
thefheavier or> hydrofluoric. acid phase- may be
recycled, as through «conduit I5,..to. alkylatorA I3.
@The :bottom fraction from.. columnr 2|, which
consists> of. hydrocarbons that are substantially
free' from .dissolved hydrogen fluoride but that
skilled
in
the. art.
v
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The partially deñuorinated hydrocarbon vmate
rial passes from defluorinator 28 through con
duit 29 to deisobutanizer 30, whereby it is sepa
rated into two fractions. The overhead fraction,
which contains isobutane, may be recycled
through valve 3| and conduit II tohydrocarbon
inlet I0, or. 4part or all of it maybe withdrawn
through valvedY outlet 32 to a kc_iesiredadditional
processing step, not shown, such .as a dehydro
genation step to produce oleñns for use in alkyla
tor I3. If a substantial proportion of. 10W-.boiling
comprise organically combinedA ?luorine, is passed 70 material other thanv isobutane„. such> as propane.
and lighter, is present in this fraction, preferably
through! conduit 2‘I.to defluorinatorv 28. Deflu~
orinator -28 may consist of -any suitable closed
chamber', containing »a .dehydrogenation-'hydro
genation-type .contact mass, through which the
hydrocarbons . may; Abe' passed. ' - Specific- -contact
at least. part offitv is passed through conduit 33
,having valvel 34 ’to depropanizer 35, wherefrom
undesired low-boilingv material is withdrawn as
an `overheadifraction. through valved outlet 36,
. 2,403,714
fraction containing about .003 per cent by weight
of fluorine may be obtained. This fraction was
'contacted with an additional quantity of bauxite
at 300° F. and a space velocity of 2.3 liquid vol
umes of hydrocarbon per volume of bauxite per
hour and at a pressure of '75 pounds per square
inch.' The fluorine >content 'o'i‘ the eiiiuent'was
found to be .0003 per cent', indicating " almost
complete removal of fluorine.
' '
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Instead of bauxite, the other contact materials
" described, such as alumina, chromium oxide, etc.,
may be used in a' manner similar’to 'that de
' >scribed above.
.. Because the invention may be .practiced other
‘Wise than as specifically described or illustrated
nherein,` and >because many _modiñcations and vari
ationswithin the spirit and scope of it will be
obvious to thoseskilled. in the art, the invention
should not be unduly restricted by the foregoing
specification and examples, butI it should be re
stricted only in accordance with the appended
n claims.
I claim:
1. The process of removing organically com
bined ñuorine from mixtures of normally gaseous
and normally liquid hydrocarbons containing said
`fluorine, which comprises subjecting such a mix
a solid, porous metal’ oxide-catalytically active
for hydrogenation and dehydrogenation reac
tions, for the further removal of organically com
bined'fluorine from said fraction.
Y
6. The process of claim .f5 in which the second
defiuorinating zone is at a» higher temperature
thanthe ñrst.
, » 7. The process of claim 5 wherein said metal
oxide isalumina in theform of bauxite and in
which the temperature in the iirst deiluorinat
ying zoneis between about 150 and 350°- F. and
in the second defluorinating zone isfhigher than
the temperature in said iirst deñuorinating zone
and is between about 200 and 400° F.
f „ 8.: Ak process for producing normally liquid hy
drocarbons substantially free from fiuorine-con
taining compoundsVwhich comprises alkylating
a low-boiling alkylatable hydrocarbonwith `an
alkylation agent in an alkylation zone in the
Apresence of va Aconcentrated hydroñuoric acid al
kylation catalyst, removingfromeiliuents of said
alkylation zone a liquid.y hydrocarbon material
containing hydroñuoric acid in solution, passing
said liquid hydrocarbon material to a fractional
distillation zone, fractionally distilling said mate
rial in said zone at a kettle temperature between
about 150 and 350° F. to remove hydrofluoric acid
ture to the action of a solid, porous metal oxide
as a low-boiling fraction, passing as a high-boil
fraction and a normally liquid fraction, andI sub
jecting the normally liquid fraction to the action
drogenation reactionsk for `altime such that exten
ing kettle product of said distillation zone an
catalytically active for hydrogenation and dehy
drogenation reactions, at a-reaction temperature 30 essentially hydro?luoric acid-free ñuorine-con
>taining hydrocarbon mixture to a ñrst defluo
'_ and for a time suiiicient to effect substantial re
rinating zone without-substantially cooling or
moval of said nuorine from said mixture and such
heating saidfraction and contacting same, at
that extensive chemical changes in the hydrocar
about the kettle temperature used in said distil
bons of said mixture are not effected,v separating
' the eilluent therefrom into a normally gaseous , lation zone, withla solid„vp_orous metal oxide .cat
' of: a second solid, porous metal oxide catalytically
active for hydrogenation and dehydrogenation re
actions, at an elevated temperature to effect fur- \
ther removal of fluorine from said fraction.
2. The process of claim 1 in which the solid,
porous metal oxide comprises aluminum oxide.
3. The process of claim 1 in which said metal
`oxide is alumina in the form of bauxite.
4. The process of claim 1 in which the temper
ature of the ñrst vcontacting step is in the range
of about 150° to 350° F., and the temperature in
the second contacting step is higher than tha't‘of
'said first contacting step and is in the range of
about 200° to 400° F.
`
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Y
alytically active for hydrogenation Vand dehy
sive chemical changes in the hydrocarbons pres
ent in said mixture are 'not effected and such
as to effect a substantial removal of fluorine from
said mixture, passing eiiiuents of _said first defluo
rinating zone> to .a separating means, separating
a low-boiling hydrocarbon fraction comprising
an unreacted lalkylatable hydrocarbon, separat
ing further a higher-boiling hydrocarbon frac
tion containing hydrocarbons produced by-said
alkylation, passing the last said fraction to a
second defluorinating ¿zone and contacting
same therein at a `temperature between about
200 and ,400° F. and higher than that used in
saidV first defluorinating zonewith asolid, po
highly branched, saturated-type hydrocarbons
which comprises subjecting a low-boiling alkyl
yatable paraffin hydrocarbon to the action of an
alkylating agent selected from the group which
consists of oleñns, alcohols, and alkyl halides Vhav
ing three to ñve carbon atoms per molecule, in
rous metal oxide catalytically active for hydro
genation and dehydrogenation reactions for a
time Sufñcient to eil’ectl no substantial chemical
conversion of the hydrocarbons present and such
that the total eiiluent from said `treatment is
essentially fluorine-free, and recovering from said
second defluorinating zone a ñuorine-free hydro
the presence of substantially anhydrous hydro
carbon alkylate so produced._
fluoric acid as a catalyst in an alkylation zone
9. In a process for producing normally liquid
hydrocarbons substantially free Yfrom fluorine
containing compounds by alkylation of a low-boil
ing alkylatable hydrocarbon in the presence of Ya
5. The process for producing normally liquid,
under alkylating conditions, separating the eiîlu
ent from said alkylation zone into a hydrofluoric
acid phase and a hydrocarbon phase, `returning
atv least part of the acid phase to ther alkylation
zone, passing the hydrocarbon phase to av frac
tionation step for removing free hydrogen fluo
ride, passing the hydrogen fluoride-free hydro
carbon material to a first defluorinating zone con
taining a solid, porous metal oxide catalytically
._ .
concentrated hydrofluoric» acid ,alkylation cata
lyst, the improvement which comprises passing
a liquid hydrocarbon material, separated from
eflluents ofsuch an 'alkylation zone and contain
ing hydrofluoric acid in solution, to a fractionalV
distillation zone, `removing vfrom said material in
active for hydrogenation and dehydrogenation re- ì . saidzone hydrofluoric acid as a low-.boiling frac
tion, Yand passing _' from said distillation zone as
actions, for the removal of a substantial propor
tion of organically combined fluorine therefrom,
debutanizing the eiñuent from said first defluori
nating zone, and passing the remaining hydrocar
bons .to a second defluorinating zone containing
Y a high-boiling fraction an essentially hydroñuoric
.acid-free i fluorine-containing hvdrocarbon mix
^ture to- a defluorinating , zone without;- substan
tially »heating or coolingsaid ¿high-'boiling frac
2,403,714.
9
.
I tion and contacting same, at about the kettle
carbon mixture to a first deiiuorinating zone
temperature used in said distillation zone, with
a solid, porous metal oxide catalytically active for
hydrogenation and dehydrogenation reactions for
without substantially cooling or heating said frac
tion and contacting same, at about the kettle
temperature used in said distillation zone, with a
solid porous contact mass comprising alumina for
a time such that extensive chemical changes in
a time such that extensive chemical changes in
the hydrocarbons present in said mixture are not
effected and such as to effect a substantial re-v
moval of iiuorine from said mixture.
the hydrocarbons present in said mixture are not
effected and such as to effect a substantial re-`
moval of tluorine from said mixture, passing ef
iluents of said first defluorinating zone to a sec
ond, fractional distillation zone, -fractionally dis
tilling said material in said second zone at a ket
tle temperature not greater than about 400° F.
and higher than that used in Asaid ñrst distilla
_tion zone to remove low-boiling paraiiins leaving
a liquid alkylate fraction, passing as a high-boil
ing kettle product of said distillation zone a sub
10. A process forproducing normally liquid hy
drocarbons substantially free fromV iiuorine-con
taining compounds, which comprises alkylating
a 10W-boiling alkylatable hydrocarbon with an
alkylation agent in an alkylation zone in 'the
presence of a concentrated hydroiiuoric acid al
kylation catalyst, removing from etliuents of said
alkylation zone a liquid hydrocarbon material
containing hydroiiuoric acid in solution, passing
said liquid hydrocarbon material to a fractional
stantially butane-free iiuorine-containing alkyl
distillation zone, fractionally distillingsaid mate
ate fraction to a second defluorinating zone with
out substantially cooling or heating said fraction
and contacting same, at about the kettle tem
perature used in said second distillation zone and
at a temperature higher than that used in said
rial in said zone at a kettle temperature between
about 150 and 350° F. to remove hydroñuoric acid
as a low-boiling fraction, passing as a high-boil
ing kettle product of said distillation zone an
iirst deiiuorinating zone, with a solid porous con
taining hydrocarbon mixture to a ydefluorinating 25 tact material comprising alumina for a time sui'
zone without substantially cooling or heating said f iicient to eifect no substantial chemical conver
-sion of the hydrocarbons present and such that
fraction and contacting same, at about kettle
the total effluent from said treatment is substan
temperature used in said distillation zone, with a
tially tluorine-free, and recovering from said sec
solid, porous metal oxide catalytically active for
hydrogenation and dehydrogenation reactions 30 ond deiiuorinating zone a substantially ñuorine
essentially hydrofluoric acid-free fluorine-co'n
for a time such that extensive chemical changes
‘ free paramnic hydrocarbon alkylate so produced.
13. The process or claim 12 in whichsaid con
in the hydrocarbons present in said mixture are>
tact masses comprise bauxite.
not effected and such as to eiïect a substantial
-
14. The process of claim 9 in which said solid,
removal of ñuorine from said mixture.
11. The process of claim 8 in which bauxite is 35 porous metal oxide comprises aluminum oxide.
15. The process of claim 10 in which said solid,
the solid,l porous material used in each said de
porous metal oxide comprises aluminum oxide.
iiuorinating zone.
16. The process of claim >9 in which said metal
12. A process for producing normally liquid
oxide is alumina in the form of bauxite.
paraiiin hydrocarbons substantially free from
17. The process of claim 10 in which said metal
iiuorine-containing compounds. which comprises 40
oxide is alumina in the form of bauxite.
18. The process of claim 5 in which said metal
alkylating isobutane with an olefln in an alkyla
tion zone in the presence of a concentrated hy
oxide y in each of said defiuorinating zones is
droiiuoric acid alkylation catalyst, removing from
aluminum oxide and in which the temperature in
the ñrst deiluorinating zone is between about 150
eiiiuents of said alkylation zone a, liquid hydro
carbon material containing hydrotluoric acid in
and 350° F. and in the vsecond deiluorinating zone
is higher than the temperature in said ñrst de
fluorinating zone and is between about 200 and`
solution, »passing said liquid hydrocarbon mate
rial to a iirst fractional distillation zone and
therein fractionally distilling said material at a
kettle temperature not greater than about 350° F.
to remove hydrofluoric acid in a low-boiling over
head fraction, passing as a high-boiling kettle
product of. said distillation zone an essentially
hydrofluoric acid-free ilumine-_containing hydro
400° F.
50
19. The process of claim 8 in whichsaid metal
oxide in each of said defluorlnatingl zones com
prises aluminum oxide.
FREDERICK E. FREY.
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