Note: Descriptions are shown in the official language in which they were submitted.
1064971
* * BACKGROUND OF T~IE INVF.NTION * *
~his invention relates to a process for producin~ an
alkylation reaction product from an isopara~:ein and an ole:Ein-
acting agent, utilizing hydrogen Eluoride ca-talysts. In one
aspect, this invention relates to a process Eor reacting lower
S molaaular weight isoparaffins with lower molecular weight ole-
fins to produce higher molecular weigh-t branched-chain hydro-
carbons suitable for use in motor fuel. In another aspect,
this invention relates to a method for reducing the alkylation
.~ ~
~64~7~
catalyst inventory requirements in a hydrogen fluoride catalyzed
alkylation process. In a further aspect, this invention relates
to a method for using two hydrogen fluoride catalyst phases, dif-
fering in acid strength, in an isoparaffin-olefin alkylation op-
eration.
Alkylation of isoparafinic hydrocarbons, such as iso-
butane and isopentane, with olefinic hydrocarbons such as propy-
lene, butylenes and amylenes, or with other olefin-acting agents
such as C3-C5 alkyl halides, etc., using hydrogen fluoride as a
catalyst is well known as a commercially important method for
producing gasoline boiling range hydrocarbons. ~he C5-Clo hydro-
carbons typlcally produced in isoparaffin-olefin alkylation op-
erations are termecl "alkylate". ~lkylate is particularly useful
as a motor fuel blending stock. It possesses motor and research
octane ratings high enough that it may be employed to improve the
overall octane ratings o available gasoline pools to provide mo-
tor fuels whiah comply with the requirements of modern automobile
; motors. High octane alkylate blending components are particular-
ly important in producing motor fuels of sufficiently high octane
when it is desired ~o avoid use of alkyl lead compounds in the
motor uel. A continuing goal in the art is to provide an econ-
omically attractive hydrog0n fluorlde catalyæed alkyla~ion proc-
ess which provicles an alkylate product having motor and research
octane ratings which are higher t~an are attainable in convention-
~5 al alkylation processes.
In commeraial isoparaffin-olefin alkylation operations
using hydrogen fluoride catalyst, generally, isobutane is the
isoparafin used and propylene, butylenes, amylenes, or a mixture
.
-2~
., .
64~73~
of these olefins, are used as the olefin-acting a~ent. In con~
ventional prior art operations, the isoparaffin, olefin-acting
agent and hydrogen fluoride catalyst are first contacted and
thoroughly admixed in an alkylation reactor, forming a reac-
tion mixture, or emulsion. After a relatively short time, re-
action of the alkylating agent is substantially complete and
the reaction mixture i5 withdrawn from the alkylation reactor
and is allowed to settle by gravity into immiscible hydrocar-
~on and catalyst phases in a settling vessel. The hydrogen
fluoride catalyst phase thus separated is returned directly
to the alkylation reactor for further catalytic use. The hy-
drocarbon phase separated in the settling operation is further
processed, e.g., by fractionation, to recover the alkylate prod-
uct and to separate unconsumed isoparaffin for recycle to the
alkylation reactor.
It has been found necessary in prior art to maintain
conditions in hydrogen fluoride catalyzed isoparaffin-olefin
alkylation operations within fairly specific ranges. For ex-
ample, conditions such as temperature, pressure, reactant and
~2~ catalyst concentrations, etc., must be carefully regulated in
order to provide an acceptable ~ield o~ high quality alkylate
product. One o~ the alkylakion conditions Eound ko be essen-
tial in produclng an alkylation xeackion product o adequate
quality has been the maintenance of a catalyst/hydrocarbon vol-
ume ratio above a minimum level in the alkylation reactor. As
used herein, the term "aatalyst/h~ydrocarbon volume ratio" means
the ratio of the volume of catalyst introduced lnto a reactor
or soaker per unit time divided by the volume of hydrocarbons,
..,_
--3--
., .
3L~6~97~
including hydrocarbonaceous alkylating agents such as alkyl
fluorides, introduced into the reactor or soaker per unit time
It has been found necessary in prior art to maintain a catalyst/
hydrocarbon volume ratio in the feeds to an alkylation reactor
of at least about 1:1, and a catalyst/hydrocarbon volume ratio
of about 1.5:1, or greater, is usually found to provide a prod
uct of superior quality. It has been found that, when lower
. catalyst/hydrocarbon volume ratios are utilized, so that the
catalyst/hydrocarbon volume ratio is less than about 1:1 and
- 10 often even when the catalyst/hydrocarbon volume ratio is less
than 1.5:1, that the olefin concentration in the catalyst be-
comes relatively high, and results in a high rate of olefin
polymerization in the alkylation reactor. It is well known in
the art that olefin polymerization is a very undesirable side
reaction, using up large amounts of valuable olefin feedstocks
and producing low octane, overly high boiling product hydrocar-
: bon. Eforts are normally made to avoid olefin polymerization
in the alkylation reactor, if possible. Thus, it has been found
essentiai i.~ prior art to maintain the catalyst~hydrocarbon ra-
tio in the alkylation reactor at a relatively hiyh level, gener-
ally about 1:1 or more, in order to provide a high ~uality alky-
late procluct and to avoid excessive consumpti.on oE olefinic feed-
stocks.
Another of the alkylation conditions found conducive to
khe production o~ high ~uality alkylate product in commercial op-
erations has been the use in the alkylation reactor of a hydrogen
fluoride alkylation catalyst haviny a relatively law acid strength
(e g., less than about 9S w~lght percent hydrogen ~luoride and
--4--
~L06497~
preferably between about 80 weight percent and about 90 weight
percent hydrogen fluoride). Higher strength hydrogen fluoride
alkylation catalyst may be used; however, the quality of the al-
kylate product produced using higher strength catalyst i5 signi-
ficantly less than the quality of alkylate produced when lower
strength catalyst, having the preferred 80-go weight percent
acid strength, is used in the alkylation reactor.
In a relatively recent modification, a reaction soaker
has been added to the conventional alkylation scheme. The hydro-
carbon reactants and hydrogen fluoride catalysts are first charged
to a reactor-cooler equipped with heat exchange means and the re-
actants and catalyst are thoroughly admixed therein to :Eorm a re-
action mixture. Within a short period o:f residence time, e.g.,
about 0.1-2 minutes, substantia]..Ly all o the olefins charged to
the reactor--cooler react with isoparaffin to form alkylate hydro-
carbons with the simultaneous ormation of large amounts of heat
energy. This heat energy is removed from the reaction mixture in
.
. the reactor-cooler in order to maintain the reaction mixture at a
fairly uniform temperature. A~ter a short ~ 2 minute residence
time in the r actor-cooler, rather than simply settling the reac-
.tion mixture as in prior art, the reac-tion mixture is passed ~rom
the reactor into the reaction soaker which generally cloes not have
heat exchange means. The reaction soaker is typically a relative-
ly large vessel equipped with perforated trays, baffle sections
or other means ~or maintaining the immiscible hydrocarbons and
catalysk ln the reaction mixtu.re in the :Eorm o:~ an emulsion. The
reaction mixture is retained in the reaction soaker or a relative-
ly long residence time, e.g., about 2-60 minutes. The reaction
.,
--5--
1[)6497~
m.ixture is then removed from the reaction soaker and passed
to a conventional settler ~or gravity separation into hydro-
carbon and catalyst phases. Xt has been found that the use
of a reaction soaker as described results in a substantial
improvement in the quality and purity of the alkylate prod-
uct in comparison with alkylation operations which employ
only a conventional reactor or reactor-cooler. Use of the
soaker has been found to provide a substantial increase in
the motor and research octane ratings of the alk~late pro-
duced. This is believed to be due primarily to isomeriza-
tion of relatively low octane alkylate hydrocarbons, such
as dimethylhexane, within the soaker to form additional
quantities of relatively high octane alkylate hydrocarbons,
such as trimethylpentanes. Use o the reaction soaker has
also been found to result in a reduction in the concentra-
tion of undesirable alkyl fluorides in the hydrocarbons
treated in the reaction soaker, substantially eliminating
the problem of fluoride contamination of the alkylate prod-
uct.
Althcugh use o the alkylation soaker as descxibed
above provides a substan~ial overall improvement relative to
conventional alkylation operations, the .lon~ residence time o~
the reaction mixture within the soaker necessitates the use of
a very large total inventory of hydrogen fluoride catalysts in
the overall alkylation opera~ion, with the major portion o the
total inventory oE catalyst in the overall system being located
within the soaker at any given time. The relatively large a-
mount of catalyst thus needed in the overall operation necessi-
.,.
--6--
~()6~9'71
tates the use of largex size equipment in several sections o~
the alkylation system. The increased cost of maintaining this
large catalyst inventory partially offsets the advantages ob-
tained by using the reaction soaker. For example, every com-
mercial alkylation operation generall.y includes a large cata-
lyst storage drum which is of sufficient size to contain all
of the catalyst used in the overall system when nece~sary. The
catalyst inventory is stored in the drum during periods when
the overall opera~ion is shut down ~or any reason. When the
catalyst inventory needed in an alkylation operation is sub-
stantially increased by the use of an alkylation soaker, the
size of the catalyst storage drum must also be increased sub-
stantially. Further, the relief valve for catalyst storage
drum and relief gas neutralization equipment must also be en-
larged along with khe catalyst storage drum. Heretofore, the
beneficial results obtained using a reaction soaker in an alkyl-
ation operation have been, to some extent, hindered by the laxg-
er catalyst inventory thus required and the atter.dant increased
investment and operating costs associated with the use of the
soaker.
Other researchers have also been concerned with the
problems caused by operating an HF alkylation zone with rela-
tively low strength HF acid. Some re~aarchers have thought
that the problem was removal of alkyl ~luorides from an alkyl-
ate. The solukion proposed was to contact the alkylate in a
contacting zone with HF acid o~ high purity. See U.S. Patents
3,763,264 (CLass 260 683.42) and 3,784,628 (Class 260-683.42).
In these
ph/ ~
.
, .
.
~S)6~9'7~
patents, the patentee contacts the alkylate, containing alkyl
fluorides, in a special contacting zone wherein the alkylate
contacts high purity HF acid. In one patent, the HF acid is
indicated as coming from the overhead of the HF acid rerun col-
umn and a separate HF fraction from the depropanizer column,
in U. S. Patent 3,763,264. Both of these HF acid sources would
be reiatively high purity, and both would be substantially free
of any organic diluent, or acid soluble oil. In U. S. Patent
3,784,628, the HF acid used is 98 wt.~ pure, though the specif-
ic source of this acid is not mentioned.
In both of these mentioned patents, the patentee is
concerned with removal of alkyl fluorides. If a refiner is
only interested in removing alkyl fluorides, the very high
acid purities suggested in these patents would be optimum.
High acid strengths promote break down of alkyl 1uorides in-
to olefins and HF acid. Unfortunately, the patentees do not
seem to appreciate the fate to be suffered by the olefins lib-
erated by the high purity HF acid. These free olefins will
very quickly react in these contacting zones, and the alkylate
formed therefrom will be of a relatively low quality. The al-
kylate will be of low quality because the HF acid used does
not contain any organic diluent or acid soluble oil, to attenu-
ate :the activit~ o the HF acid catalys~. ~he Ilet e~ect o~
such an operation will be to increase slightly the end point of
the gasoline, and slightly lower the octane number of the al~yl-
ate.
The process o this invention helps eliminate such
problems and may be used to provide an alkylation operation
having a substantially reduced catalyst inventory xequirement
- \
1064~317~L
while the high quality product obtained by employing a soaker
is further improved.
Although better quality alkylate is produced when
relatively low strength (~0-90 weight percent) hydroqen fluo-
ride catalyst is employed in the alkylation reactor, it has
been found that improved results are obtained when a higher
strength (e.g., greater than 90 weight percent, and prefer-
a~ly 90 to 95 weight percent) hydrogen fluoride catalyst is
employed in an alkylation soaker. Thus, in an optimum system,
lower strength hydrogen fluoride catalyst would be utilized in
the alkylation reactor while higher strength hydrogen fluoride
catalyst containing organic diluent would be utilized in the
soaker. Heretofore, use of two distinct hydroc~en fluoride
catalyst phases, differing in acid strength, in an alkylation
operation employing an al]cylation soaker has not been possible,
since the reaction mixture of hydrogen fluoride catalyst and
hydrocarbons has been passed directly rom tlle alkylation re-
actor-cooler into the soaker, the same hydrogen fluoride cata-
lyst phase being used ~oth is the reactor-cooler and the soak-
er. The process of the present invention provides an economi-
cal ancl convenient method Eor employing two hydro~en fluoride
catalyst phase8, diPferlng in acid strencJth, in an alkylation
operation using a soaker, while avoiding produc-t degradation
which would occur if an organic diluent free acid was used in
a soaker.
* * SUMM~R~ OF TIIF, INVI,NTION * *
Accordingly, the present invention provides a process
for producing an alkylation reaction product from an isoparaf-
fin and an olefin, WhiCII comprises the steps of: ~a) reac~ing
1~i6~9~
said olefin with said isoparaffin in admixture wi~h a relative-
ly low strength hydrogen fluoride catalyst containing 75 to 95
wt. ~ HF at a catalyst to hydrocarbon ratio of 1:1 to 5:1; (b~
settling the resultant reaction mixture to separate the same in-
to a hydrocarbon phase and a catalyst phase; (c) commingling
with said hydrocarbon phase, without further addition of olefin,
a relatively high strength catalyst o hydrogen fluoride and or-
ganic diluen~t containing 90 to 98 wt. ~ HF, and more HF than
contained in said relatively low strength catalyst in a lower
10' catalyst to a hydrocarbon volume ratio than step ~a); (d~ in-
troducing the resulting mixture into a soaking zone a~d therein
isomerizing lower octane alkylate hydrocarbons to higher octane
alkylate hydrocarbons, converting alkyl fluorides into high qual-
ity alkylate an~ ~IF acid, by maintaining the last mentioned mix-
ture in the soaking zone at a temperature of 50 to 120 F for 5
to 20 minutes; (e) separating the eEfluent oE the soaking zone
irlto a second hydrocarbon and a second catalyst phase, and; (f)
recovering said alkylation reaction product from said second hy-
drocarbon phase.
The present invention provides a particularly advan-
tageous method for utilizing in an alkylatlon operation t~o
hydro~en fluoride catalysts o di~erent acid aoncentrations,
in order to provide opkimum conditions Eor the production oE
hi.gh-quality alkylate, not only with respect to an alkylation
reactor, but also with respect to an alkylation soaker. In ad-
dition, by employing a ~elat.ively low catalyst/hydrocarbon vol-
ume ratio in the feed to the alkylation soaker in addition to
employing the desirable high strength catalyst, catalyst inven-
--10--
~0~9~7~
tory requirements may be reduced substantially by using the
present process with a simultaneous improvement in the qual-
ity of the alkylate product produced.
Further objects, embodiments and advantages of the
process of the present invention will be apparent to those
skilled in the art from the following description of the at--
tached drawing and detailed description of the invention.
* * DESCRIPTION OF THE D:E~AWING * *
The attached drawin~ is a schematic illustration of
one embodiment of the process of the present invention. In
the embodiment illustrated, the isoparaffin utilized is iso-
butane a~d the olefin-acting agent utilized comprises a mix-
ture of propylene and butylenes. The scope of the present
invention is not limitecl to the embodiment thus depicted. Va-
rious other suitable reaatants and embodiments will be apparent
to those skilled in the art from the description hereinafter
provided.
Referring to the drawing, conventional isobutane al-
kylation fe~dstock, comprising about 95 weight percent isobu-
tane, i5 introduced into the operation via condui-t 1. ~onven-
tional oleEinic alkylation Eeedstock, comprising propylene and
butylenes, is introduced into the process by conduit 2 and
cha~ged into admixture With the isobutane Eeed in conduit 1.
The resulting hydrocarbon reactor charge stream is passed fur-
ther through conduit l and through conduits 3 ancl 4 into allcyl-
ation reactor~cooler 5. Multiple conduits are employed for
charging the hydrocarbon reactor charge into reactor-cooler 5
in order to effect efficient mixing of the reactant hydrocar~ons
--11--
~6497~
with hydrogen fluoride alkylation catalyst and to prevent gen-
eration of undesirably large amounts of heat in any particular
section of reactor-cooler 5. Conventional hydro~en fluoride al-
kylation catalyst, comprising about 85 wei~ht percent hydrogen
fluoride, is charged into reactor-cooler 5 via conduit 11. The
hydrocarbons and catalyst are thoroughly admixed in reactor-cool~
er 5 to form a reaction mixture, or emulsion. Substantially all
of the olefins charged to reactor-cooler 5 undergo the alkylation
reaction with isobutane in a relatively short time, with the si-
,10 multaneous release of the heat of reaction. In order to remove
the heat of reaction, cooling water is passed into reactor-cool-
er 5 via,conduit 6 and is passed in indirect heat exchange with
the reaction mixture using heat exchange means not shown. Used
cooling water is withdrawn from reactor-cooler 5 via conduit 7.
Alkylati,on conditions maintained in reactor-cooler 5 include a
temperature oE about 90F., a pressure sufficient to maintain
liquid phase operations, and a contact time of about 1 minute.
Hydrocarbons and catalyst are charged to reactor-cooler 5 at
- relative rates sufficient to provide a catalyst/hydrocarbon vol-
ume ratio of about 1.5:1 in the reaction mixture in reactor-
cooler 5. Reaction mixture which is substantially ~'ree from
unreacted olefins, and which contains primarily isobutane, al-
kylate and hydro~en Eluoride catalyst, is withdrawn from reac-
tor cooler 5 via conduit 8 and passed into settler 9. The re-
action mixture is allowed to stand without a~itation in settler
9, allowing the hydroge~ fluoride catalyst to form a heavier
phase and the hydrocarbon components o the reaction mixture
to form a lighter phase. The catalyst phase is withdrawn from
.
,.
, -]2-
10649~1
the bottom of settler 9 via conduit 10. Catalyst Erom conduit
10 is preferably passed into the higher s-trength catal~st phase
used in the soaker-settler system described hereinafter. In
such eases, valve 16 is opened suiciently to allow the de-
sired amount of lower strength cataly~t to flow from conduit
10 through eonduit 12. The low s-trenqth acid from conduit 10
is a convenient source of orgànic diluent to attenuate the ac-
tivity of higher strength acid in the soa]cer-settler.
In commercial allcylation operations, it is necessary
to treat, continuously or intermittently, a portion of the used
alkylation catalyst for removal from the catalyst of excessive
amounts of non-acid catalyst components and impur.ities (such as
water and hydrogen fluoride-soluble organie eompounds) in order
to maintain the desired aeid strength in the catalyst. Sueh
reyeneration of hydro~en ~luoride al];ylation catalyst is con-
ventional, and its pxaetiee well known to those skilled in the
art. In the embodiment of this invention illustrated in the
drawing, regeneration is aeeomplished by withdrawing a small
slip stream of catalyst rom eonduit 11 by way of eonduit 13
and passing the eatalyst stream in conduit 13 to conventional
regeneration means not æhown. The primary portion O:e the eat-
al~st stream in eonduit 11 is reeyeled tc reaetor-eoole.r 5 Eor
eatalytie use as deseribed a~ove Regenerated, high strength
eatalyst whieh is reeovered from the regeneration operation, is
passed baek into the system as deseribed hereinafter in order
to upgrad~ the strength of the hydrogen fluoricle cat~lysts used.
Referring ac3airl to settler 9, the lighter hydrocarbon phase
therein is withdrawn vla conduit 14. Iligh strength hydrogen
fluoride eat~lys-t, comprising a~out 95 weiclht perc;ent hydroqen
` -13
~L~6~97~
fluoride, from conduit 15 and the hydrocarbon stream from con-
duit 14 are admi~ed in conduit 17 and ch~rged to soaker 1~.
The admixed hydrocarbons and high strength catalyst are charg-
ed to soaker 18 at a catalyst/hydrocarbon volume ratio of a-
bout 0.1. Soaker 18 contains several perforatecl trays which
serve to maintain the high strength catalyst and hydrocarbons
charged to soaker 18 in an emulsified or dispersed state of ad-
mixturè. The temperature and pressure maintained in soaker 18
are approximately the same as the temperature and pressure em-
ployed in reactor-cooler 5. After a contact time of about 10
minutes in soaker 18, the admixed hydrocarbons and high strength
catalyst are withdrawn via conduit 19 and passed into settler
20. In settler 20 the admixed high strength catalyst and hydro-
carbons are settled in the conventional manner into separate
catalyst and hydrocarbon phases. The li.ghter hydrocarbon phase
is withdrawn from settler 20 via conduit 21 and is -then passed
to further conventional ractionation and product separation
operations not shown. The heavier, high strength catalyst
phase i9 withdrawn from the bottom of settler 20 via condult
22. A relatively small portion of the h.igller strenyth cata-
lyst stream in conduit 22 is passed into condui-t 25 ln normal,
steady state opcrati.ons, while tlle major port.ion .is p~5~ecl in-
to conduit 23. In such normal, steady state operation of the
system, sufficient high strength catalyst is passed through
condui-t 25 and combined with the lower strength hydrogen flu-
oride alkylation ca-talyst in conduit 11 to replace catalyst
and dissolved hydrogen fluoride which are removed or lost
from the lower strength catalys-t which is circulating between
-14-
1~64971
reactor-cooler 5 and settler 9. For example, some of the low-
er strenyth catalyst is removed from conduit ll via conduit 13
and passed to regeneration, as described above. Further amounts
of hydrogen fluoride are lo~t from the lowe~ strength catalyst
system as a solution in the hydrocarbon phase removed from set-
tler 9 via conduit 14. Thus, the high strength catalyst charged
to conduit 11 through conduit 25 is utilized both to maintain
the lower strength alkylation catalyst at the desired acid s-trength
and also to replace any hydrogen fluoride which is removed from
the lower strength alkylation catalyst circulation system. Refer-
ring aqain to the hiqher strength catalyst system, substantially
pure hydrogen fluoride is introduced into the svstem by was~ of
conduit 15. The substantially pure hydrogcn fluorlc'e charqecl in-
to conduit lS may be freshly introducecl but preEerably is provided
from the conventional regeneration operation and from hydrogen Elu-
oride recovered from conventional fractionation and procluct puri-
fication schemes in the alkylation system. The major portion of
the high strength catalyst phase which is removed from settler 20
via condl;t 22, is passed through conduit 23 and commingled with
the freshly intxoduced, substantially pure hydr.o~en ~luoride in
conduit 15. The hi~h strength catalys-t in conduit 15 is passed
~urther lnto adm.ixture with hydrocarhons in condulk 17 as de
scribed ahove. A relatively small portion of the catalyst stream
circulating through conduits lO and ll is charged via conduit 12
into conduit 15. I:e organic dilllent is adcled to the acid ln the
soaker-settler from arl outside source, e.g., the bo-ttoms frac-
tion of the HF acid regenerator, then valve 16 in line 12 may
be closed.
-15-
~1~6a~
In cases where little or no llydrogen fluoride is being
removed from the lower strength catalyst phase circulating be-
tween reactor-cooler 5 and settler 9, valve 26 may be shut off
completely for some time, and thus all the high strength cata-
lyst will be charged through conduit 23 and conduit 15 back in-
to soaker 18. Some conventiona]. equipment and steps which are
required for the operation of the embodiment described in the
foregoing have been omitted from the drawing and the descrip-
tion thereof. For example, certain pumps, valves, etc., may
be needed in order to operate the described embodiment. The
use and placement of such conventional items will be obvious
to those skilled in the art.
* * DETAILED D~SCRIPTION OF TH~ INVENTION * *
.. _ . .. . . .
The alkylation process of the present invention may
be applied, in general, to the alkylation of isoparaffins, par-
ticularly C4-C6 isoparaffins. The preferred isoparaffins are
isobutane and isopentane, particularly isobutane. A mixture
of two or more isoparaffins may also be employed, if desired.
~ suitabl~ lsoparaffin feedstock for use in the present proc-
ess may contain some nonreactive contaminants such as normal
paraf~ins. ~or example, a conventional commercial isobutane
alkylation feedstock generall~ contalns about 95 weight per-
cent isobutane, ~ weight percent normal butane and 1 weight
percent propane. It is well known in the art that the iso-
paraffin employed in an alkylation system is generally re-
cycled and thus may contain substantiai amounts of contamin~
ants built up by recycle to concentrations in excess of a
fresh feedstock.
-16-
.. .
7~
Olefin-acting compounds which are suitable for use
in the process of the present invention include C3-C6 mono-
olefins, alkyl halides, or mixtures thereof. C3 C5 olefins
are preferred. The process of the present inventlon may be
applied to the alkylation of mix-tures of two or more olefin-
acting compounds with the same benefits and improvements as
would be obtained in using a single olefin-acting compound.
For example, many conventional olefin feedstocks utilized in
commercial alkylation operations contain mixtures of propylene
and butylenes, or propylene, bu-tylenes and amylenes. ~pplica-
tion of the present process to such olefin mixtures results in
improvements in quality of the products obtained which are e~ual
to the improvements obtained uslng a sin~le olefin. Simi.larly,
a mixture of C3-Cs alkyl halides and oLeEins in any proportion
is also suitable in many cases, or example, when the halide is
~luoride. The particularly preferred C3-Cs olefin feedstocks
are conventionally derived from petroleum refining processes
such as catalytic cracking and may contain substantial amounts
~ of saturates, lighter and heavier olefins, etc. Olefin feed-
stocks derived from such conventional sources are suitable oruse in providing the ole~in--acting aqent ~Ised in the present
process.
~ he low strenc.tth hydro~en Eluoricle cata:Lyst ~mpLoyed
in the present process to react the isoparaffin and the alkyl-
atlng agent in the alkylation reactor may suitably be any con-
ventional hy~rocJen eluoricle calalyst used in isoparaEEin~oleEin
alkylation operations in prior art. Such conventional hydrogen
fluoride catalysts contain rom about 75 to about 95 weight
,~ ~
~ -17-
.
.
~l~6~7~
percent of titratable acid; however, a titratable acid content
of between about 80 and about 90 weight percent in the alkyla-
tion catalyst has been found to give best results. Such con-
vent.ional hydrogen fluoride catalysts contain less than about
5 weight percent water, with less than about 1 weight percent
water being preferred. The remainder of the conventional cata-
lyst~is made up of hydrogen fluoride-soluble organic diluent
compounds. In prior art, the titratable acid strength in hy-
drogen fluoride alkylation catalysts has bee~ maintained at
the desired level by continuously or intermittently withdraw-
ing a small amount o:E the catalyst from circulation in the re-
actor-settler sys-tem and passing the withdrawn portion of cata-
lyst to a catalyst regeneration system. In a conventional cat-
alyst regeneration system relatively pure hydrogen fluoride is
separated from a constant boiling mixture of water and hydrogen
fluoride and from heavy, hydrogen fluoride-soluble organic com-
pounds such as polymers and organic fluorides. The relatively
pure h~drogen fluoride pxoduced by conventional regeneration
has, in pri.or art, been passed directly back into the primary
catalyst phase which ls in ciroulation in the reactor~settlex
system. By adding a controlled amount Oe pure hydrogen Eluo-
ride tc) th~ ci.rculatln~ catalysk and simu.ltan~ou~ly withclraw-
ing a controlled amount of the dilu-ted catalyst, titratable
acid strength in the catalyst has been maintained hy compen-
sating eox c.lilut.ion and contamination o:E the ca-talyst. Cata-
lyst contaminatlorl and d.ilution are caused at least in part
by water in`the hydrocarbon reactant ~eedstocks, polymer for-
mation in the alkylation reactor, etc., which cause buildup
,.,
.
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~L~64~7~
of diluents and contaminants in the circulating catal~s~ at
a slow but relatively constant rate.
The amount of high strength catalyst required to be
admixed with the lower strength catalyst to maintain the ae-
sired material balance and acid strength in the lower strength
catalyst phase will vary according to the respective strengths
of the two catalyst phases, the rate of ailution of the low~r
strength cataly~t phase, etc., and will be obvious to those
skilled in the alkylation art.
A large number of alkylation reactors suitable for
use in the process of this invention are known in the art.
For example~ but not by way of limitation, the alkylation
reactor-coolers described in U. S. Patent 3,456,033, ~. S.
Patent 3,469,949 and U. S. Patent 3,501,536,
may suitably be em-
ployed in the present process. Particular alkylation condi-
tions necessarlly associated with the use of a particular al-
kylation reactor, or reactor-cooler, such as those described
in the above-listed patents or in connection with other suit-
able conventi.onal alkylation reactors, are also well known and
may be used in embodiments o~ the present invenkion in connec-
tion with th~ detailed descript~on o~ the alkylation conditions
utilized in a reactor-cooler which are provided hereinafter.
Alkylation conditions employed in the reactor-coolex
in the pre~ent process include a temperature of about 0F. to
about 200F., a pressure sufficient to maintain the reactants,
catalyst and reaction product in the liquid phase, a catalyst~
hydrocarbon volume ratio of about 1:1 to about 5:1 or more,
--19--
;497~
and isoparafEin/olefin mole ratio of about 6:1 -to about 30:1
and a contact time o about 0.1 minute to about 5 minutes. When
the preferred reactants, isobutane and C3-C5 olefins are em-
plo~ed, preferred alkylation conditions include a temperature
of about 50F. to about 125F., a catalyst/hydrocarbon volume
ratio of about 1.5:1 to about 2.5:1 and a contact time of a-
bout 0~2 minute to about 2 minutes. The hydrogen fluoride al- -
kylation catalyst is generally immiscible with the isoparaffin
reactant and with the alkylation reaction products formed in
the alkylation reactor, so that various means for mixing or
agitation of the lower strength catalyst phase and the hydro-
carbons are generally employed in the alkylation reactor in
order to provide the reaction mixture, or emulsion, oE catalyst
and immiscible hydrocarbons. Some heat removal means is gen-
erally necessary for satisfactory operation of the alkylation
reactor. Various means for accomplishing heat withdrawal and
temperature control in the alkylation reactor are known in the
art, any of which may suitably be employed in the present proc-
éss. For ~xample, in a preferred embodiment heat generated as
heat of reaction in the alk~lation reactor may be removed from
the reaction mixt-lre by use o~ a combination reactor-cooler,
Which includes indirect heat exchancJe between a cool.ing fluid
and the reaction mixture within the reactor-cooler. Precooling
of the hydrocarbon reactants or hydrogen 1uoride alkylation
catalyst has ~lso been utilized in orc~er to maintain the de~
sired temperat~lre in the reactor-cooler.
A variety of vessels which are suitable or use in
settling the reaction mixture to separate a hydrocarbon phase
-20-
~0~97J
from the lower strength catalyst phase are well known in the
alkylation art. lhe effluent from the alkyla-t.ion reactor is
conventionally settled to separate a hydrocarbon phase from
the alkylation catalyst. The hydrocarbon phase contains the
al~ylation reaction product and excess isoparaffin. The hy-
drocarbons and catalyst are maintained at about the same tem-
perature and pressure in the settling operation as are used
in the alkylation reactor. In prior art al}cylation operations
utilizing a soaker, the reaction mixture has been passed direct-
: ly from the alkylation reactor into the soaker. The reaction
: ~ mixture removed from the soa~er has then been char~Jed to a con-
v~ntional settler for complete separation o-E the cakalyst and
hydrocarbon phases. In the present process, in contrast, the
hydrocarbon eEfluent rom the alkylation reactor is completely
lS separated :Erom the lower strength catalyst phase b~ settling.
The lower strength catalyst phase is then recycled directly to
the alkylation reactor, while the resultin~ hydrocarbon phase
.
is passed to the alkylation soaker where it is admixed with the
higher s~rc;lgth hydrogen fluoride catal~st described hereinater.
The hydrocarbon phase .recoverecl Erom the ~.irst settl-
ing operation i.n the ~resent process is aclmixecl with a h~dro~en
Eluoride cataly~t pllase contai.nin~ :~rom abo~lt 90 we.i~ht percent
to about 98 weight percent titratable acid in an alkylation soak-
er. The hydrogen fluoride catal~st phase emplo~ed in the soaker
prefe.rably contains about 95 we.igllt pe.rcent titratable acid, or
more, and in any case it is esserltial to the present process
that the catalyst phase empl.oyed in the soaker contain a higher
titratable acid content than the acid stre~gth i.n the lower
.. . ~
-21-
.
~LO~i4~7~L
strenyth catalyst phase which is utilized in the alkylation
reactor. The relatively high acid content of the high strength
hydrogen fluoride catalyst phase used in the soaker is prefer-
ably provided during normal operation of the process by charging
substantially pure hydrogen fluoride from various conventional
sources into the high strenqth catalyst phase, as needed to main-
tain high acid strength. For example, substantially pure hydro-
gen fluoride may be obtained as fresh acid from a source outside
the alkylation operation, as well as from conventional catalyst
regeneration systems which form a normal part of al~ylation op-
erations. Substantially pure hyclxogen fluoride may also be re-
covered as a separate phase which settles out in various receiv-
ing vesse~s, settlers, etc., in the conventional ~ractiollation
and purification equipment used in alkylation operatiol-s. Such
sources o~ suhstantially pure hydrogell Eluoride are well known
to those skilled in the alkylation art. By employing the high
stxength hydrogen fluoride catalyst phase in the alkylation soak-
er, the beneficial effects on the cluality of -the alkylate prod-
uct whicll are obtained when a soaker is employed are actuall~
improvecl over conventional use oE a soaker.
It is also e~ential to -the prac-tice of -the present
invention th~t the high~r strength ~cicl contain su~icient or
ganic diluent to attenuate the high activity o~ pure HF acid.
The acid must contain 2 to 10, and preferably about 5 wt. % or-
~nic diluent ~or optimum operation of the soaker-settler. The
high strength catalyst is particularly eEfective in producing
the desired isomerization o~ lower oc-tane alkylate hyclrocarbons
to provide higher octane products. The high strength catalyst
-22-
6~97~
is also highly effective in eliminating undesirable alkyl fluo-
rides which may be present in the alkylate containing hydrocar-
bons. Such alkyl fluorides are otherwise difficult to separate
from the alkylate product, since they often have a boiling ra~ge
. similar to that of the alkylate. By maintaining a distinc-t and
separate catalytic phase of high strength hydrogen fluoride cat-
alyst and by using conventional sources of relatively pure hy-
drogen fluoride and conventional organic diluents to provide
such a high strength catalyst phase, the present process pro-
vides a convenient and economical method for utilizing the highstrength catalyst obtainable in an alkylation operation.
Although not essential to the operation of the present
process, the use of a separate high stre~gth catalyst phase in
the soaker is particularly advantageous when it is desired to
use a low catalyst/hydrocarhon volume ratio in the alk~lation
soaker in order to reduce catalyst inventory re~uirements in
the overal~ alkylation operation. As discussed above, high
strength catalyst is more effective in the alkylation soaker
than i9 conventional low acid strength catalyst; however, the
low acid strength catalyst provides superior results when used
as an alkylation catalyst, Using prior art alkylation methods,
it has not been possible to employ more than one catalys~ phase
in the overall alkylation operation, so that max.imum e:E:Eiciency
in both the alkylation reactor and the alkylation soalcer could
not thereby be obtained. By employing the present process, best
use can be made o:E both the alky].ation reactor and the soaker.
For example, optimum use o:E -the alkylation reactor requires a
relatively large amount of lower strength hydrogen fluoride
.
-23-
,
~0649~7~
catalyst, while a relatively small amount of hi~her strength
hydrogen fluoride catalyst is preEera~le in the soaker. By
utili~ing the high strength catalyst phasè at a relatively
low catalyst/hydrocarbon volume ratio in the soaker, the pres-
ent process can be utilized to avoid the very large overall
catalyst inventories which have characterized prior art use
of alkylation soakers. The use of high strength acid, atten-
uated with organic diluent, in the soaker-settler also avoids
the formation of undesirable, high end point alkylate which
occurs in prior art methods usin~ an organic di.luent free HF
acid to contact al~yl fluorides..Further, the high s~ren~th
acid o~ the present invention will promote isomerization of
alkylate, as the acid contains organic cliluent. A pure H~
acid catalyst does not act as a satis:Eactory isomeriæation
catalyst in this service. At the same time, alkylate qua.l-
ity is improved through the use of higher s-trength catalyst,
so that the low catalyst/hydrocarbon volume ratio employed in
the soaker results in no adverse effects on alkylate quality.
In the present process, after the hydrocarbon phase
has been separated -from the lower stren~th alkylation catalyst,
the hydrocarbon phase and the higher strength hy~rogen Eluoride
catalyst are chargea to the soa]cer at a aatal~rst/hydroca.rbon
volume ratio betweerl about 0.01 and about 5:1. PreEerably the
catalyst/hydrocarbon volume ratio of the catalyst-hydrocarbon
mixture passed into the soaker is maintained within the range
~rom about 0.01:1 to about l:l, and a particularly preferred
range of operation in the present process includes a catalyst/
hydrocarbon voLume ratio between about 0.05:1 and about 0.15;]..
~C~69~97~l
The settled, lower strength catalyst phase is prefer-
ably recycled from the first settler directly back to the alkyl-
ation reactor. Since only ~ small amoun-t of the lower strength
hydrogen fluoride catalyst used in the alkylation reactor in
the present process is employed in the soaker, to supply organ-
ic diluent to the higher strength acid therein, a very signifi-
cant reduction in overall catalyst inventory requirements may
be obtained when the preferred, low catalyst/hydrocarbon volume
ratio is employed in the alkylation soaker. The benefits ob-
tained by employing the soaker in the alkylation operation of~
the present process are fully obtained by passing the catalyst-
hydrocarbon mixture into the soaker at a low catalyst/hydrocar-
bon volume ratio, and the operation o~ the soaker is improved
by the use of the hi~h strength cataly~t phase in the soaker.
By using the preferred, low catalyst/hydrocarbon volume ratio
in the soaker alone, and not in the alkylation reactor, the re-
quired high catalyst/hydrocarbon volume ratio may be maintained
in the alkylation reactor in order to prevent,a high degree of
olefin ~olvmeriæation in the reactor~ while simultaneously the
benefits o~ the soaker are improved and the clrawb~cks oE prior
art use oE allcylation soakers are obviated.
The soaking zone employed .in the presen~ process may
be any suitable alkylation soaker or any o~her suitable vessel
known to those skilled in the art. For example, the soakers
shown and describecl in U.S. Patents 3,560,587 and 3,607,970
may suitably be employed i~ the present process. A variety
of other vessels which may suitably he employed as an alkyla-
tion soaker in the present process will also be obvious to
..
-25-
: ~ .
~649~
those skilled in the a~t. Conventional alkylation soa]cers
are typically vessels equipped with perforated trays, baffle
sections or the like in order to maintain the admixed high
strength catalyst and hydrocarbons which are charged there~
to in the form of a fairly homogenous mixture or emulsion
'for the desired contact time in the soaker.
Soa~ing conditions in the present process in addition
to the catalyst/hydrocarbon volume ratio discussed above, also
include a temperature of about 50F. to about 120F., a pre~-
sure sufficient to maintain the catalyst and hydrocarbon charged
to the soaker in the liq~id phase, and a contact time of about
2 minutes to about 60 minutes in the soaker. Pre~erably, a con-
tact time between the high strength catalyst and hydrocarbons
in the soaker of about 5 minutes to about 20 minutes is employed.
The mixture of catalyst and hydrocarbon removed from
the soaking zone after the desired residence time is passed to
a conventional settler, wherein the soaker effluent is settled
in the conventional manner to separate the high strength cata-
lyst from the hydrocarbon phase. The settled hydrocarbon phase
recovered from the second settler is passed to further conven-
tional separation operations, such as ~ractionation, in order
to recover the alkylate product and to sepa~ate excess isoparaf-
Eins or further conventional recycle to the alkylation xeactor.
~ The hi~h strength catalyst phase recovered by settl-
ing the effluent from the soaker is generally recycled to the
soaker for furtller use as described above. A portion of the
high s-trength catalyst ~hase may be admixed with tlle lower
strength catalyst phase used in the alkylation reactor so as
-26-
~6~g7~
to maintain the desired acid streng-th in the lower stre~gth
catalyst phase and also -to provicle a su;Eeicient makeup of
lower strength catalyst to oefset any losses of the lower
strength catalys-t to e.g., regeneration, solution in settled
hydrocarbons, etc. In a preferred embodiment of the present
process, controlled amounts of the lower strength catalyst
phase are mixed with the higher strength catalyst phase in
order to provide the necessary volume of higher strength cat-
alyst. However, it is essential to maintain the lower strength
catalyst phase essentially separate from the higher strength
catalyst phase during normal operations in order to maintain
the two distinct catalyst phases at differing titratable acid
strengths.
The alkylation reaction product produced in the pres-
ent process when the preferred isobutane and C3 and C~ olefins
reactants are employed, include C7 and C8 saturated hydrocarbons
resulting ro~ the alkylation reaction of the isobutane with the
o~efins. The primary reaction products include, ~or example,
dimethylhexanes and trimethylpentanes. It is well known in the
; 20 ar~ that more highly branched hydrocarbons possess superior prop-
erties as motor fuel components, and the present invention is di-
rec~ed, in part, to providing an alkylation reaction product con-
tainin~ a higher rakio O;e more hi~l~ly b~anched hydrocarbons, s~lch
as trimethylpentanes, to less branched hyclrocarbons, such as di-
methylhexanes. The foregoing is accomplished through the use of
the combina~ion Oe the alkylation reactor and the al~ylation soak-
er with the use oE two separate hydrogen Eluoride catalyst phases
difering in titratable acid strength. Thus, optimum alkylation
1~64~71
conditions are maintained both in the alkylation xeactor and
in the soaker. In addition, use of -the higher strength hydro-
gen fluoride catalyst in the alkylation soaker results in im-
proved operation of the soaker when the catalyst/hydrocarbon
volume ratio used in the soaker is maintained even at a very
low level. Use of the low catalyst/hydrocarbon volume ratio,
in turn, results in a substantial reduction in the overall
catalyst requirements of the alkylation process in contrast
to prlor art alkylation operations employiny a soaker. It is
thus apparent that the present invention provides a process
for producing superior motor fuel alkylate produc-ts by a meth-
od more economical and convenient than has been availahle in
the prior art.
* * ILLUSTR~TIVE EMBODIMENT * *
In orde~r to illustrate one preferred mode of opera-
ti.on of the process of the present invention, a system iden-
tical to that shown in the attached drawing is employecl. Con-
ventional fresh and recycle isobutane alkylation f~ed and con-
ventional ~resh butylenes al]cylation ~eecl are passecl into the
system through conduits 1 and 2 at the rate of ~6,000 barrels
per day and at arl isobutane/butylene mole ra~.io of about 10:1.
~he hyclrocarboll reactor charcJe stream thus ~ormed is passed
through conduits 1, 3 and 4 into reactor 5. Low strength
(sli~htly greater than 85 weight percent titratable acid) hy-
drocJen ~luoride alkylation catalyst is passed into reactor S
by way of conduit l:l at the rate of 67,500 barrels per day.
The catalyst and hyclrocarbons charged to reactor 5 are con-
tacted and admixed therein for a con-tact time of 0.5 minute
-28-
.
1f[~64~
at a temperature of 90F. and a pressure sufficient to main--
tain the hydrocarbons and catalyst a.s liquids. The reaction
mixture of catalyst and hydroc~rbons form~d in re~ctor 5, sub-
sequent to the reaction of substantially all -the olefins charg-
5 ` . ed to the reactor, is withdrawn from reactor 5 and passed throughconduit 8 into~settler 9. rrhi~ latter step is in contrast to
prior art alkylation operation utilizing a soaker, wherein re-
action mixture withdrawn from the alkylation reactor is passed
directly to a soaker. In the present process, reac-tion mixture
is continuously settled in settler 9 to separate the lower strength
catalyst from a hydrocarbon phase. Settled, lower strength cata-
lyst is withdrawn from settler 9 at the rate of 67,050 barrels
per day, and passed through conduit 10 into conduit 11. Valve
16 passes 375 barrels per day o~ lower strength catalys-t to the
soaker-settler via line 12. A s].ip stream of lower strength cat-
alyst is withdrawn rom conduit 11 by way of conduit 13 at the
rate of 350 barrels per day, and is passed to catalyst regener-
at~ion means not shown. A settled hydrocarbon phase, containing
primarily isobutane, hydrocarbon alkylate ancl some dissolved hy-
drogen fluoride, is withdrawn rom set~ler 9, via conduit 1~ atthe rate of ~0,000 barrels per day isobutane, 5,000 harrels per
day alkylate hyclxoearbon~ and 4$0 ha.rrels p~r day clissolved hy-
drogen fluoride. The hydrocarbon stream in concluit l.~ is passed
into conduit 17 and admixed therein with~about 95 weight percent
2S hydrogen fluoride) hydxogen fluoride from conduit 15 which is
passecd into conduit 17 at the rate o:E about 4050 barrels per
day. The mixture of hydrocarbons and high strength hydrogen
fluoride catalyst is passed from conduit 17 into soaker 18.
-29-
,
~696~7~
In soaker 18, the admixed high strenyth catalyst and hydro-
carbons are maintained in intimate contact for a contact time
of about lO minutes at a temperature of about 90F. and a pres-
sure sufficient to maintain the hydrocarbons and catalyst as
liquids. ~sing the present process, a substantially smaller
amount of hydrogen fluoride may be used in a soaker than has
heretofore been possible in prior art alkylation operations
including a soaker. Use of high strength catalyst in soaker
` 18 provides optimum results in the soaker, while the relative-
ly high (1.5:1) catalyst/hydrocarbon volume ratio utilized in
reactor 5 need not also be used in soaker 1~, as has been nec-
essary in prior art. The admixture of high strenc3-th hydroqen
fluoride catalyst and hydrocarbons is removed from soaker l~
after about lO minutes contact time and passed through conduit
19 into settler 20. In settler 20, a high strength, about 95
wt.% hydrogen fluoride phase is separated from a hydrocarbon
phase. The hydrocarbon phase separated in settler 20 is re-
moved via conduit 21 and passed, at the rate o 40,000 barrels
per day isobutane, 5,000 barrels per day alkylate hydrocarbons
and 450 barrels per day dissolvecl hyclro~en Eluc.).rid~, to conven-
tional fractionation and puriEication operations for recovery
of the alky.late product and ~or separatioll and recycle o~ iso-
butane and hydrogen fluoride. The high strength catalyst phase
formed in settler 20 is removed via conduit 22 at the rate of
2$ 4,050 barrels per day. Valves 24 ancl 26 are adjusted so that
a first portion of the hydrogen fluoride s.tream in concluit 22
is passed into conduit 23 at the rate oE 2,925 barrels per day
and a second portion is passed into conduit 25 at the rate of
-30- ~
~6497~
1125 barrels per day. The high strength catalyst in conduit
25 is passed into conduit 11 in order to replace hydrogen flu-
oride lost from the lower strength catalyst phase employed in
reactor 5. 5ubstantially pure hydrogen fluoride is passed in-
to the operation via conduit 15 at the rate of 750 barrels per
day. The substantially pure hydrogen fluoride passed into con-
duit.15 is provided by conventional regeneration of the low
strength catalyst removed from the operation via condui-t 13
and by c.onventional recovery of hydrogen fluoride dissolved
in the hydrocarbon phase which is passed out of the operation
via conduit 21. The high streng-th catalyst phase in conduit
23 is passed into conduit 15 and the resul-ting catalyst stream
is passed into conduit 17 at the rate of 4,050 barrels per day.
* * *
-31-
