Note: Descriptions are shown in the official language in which they were submitted.
~ _ACX&ROVN~ O THE INV~NTION
`~ Catalytic alkylat~on o~ l~obutane 1~ well ~nown in
the art9 b~ng the union Or an ole~ln wlth i~obutane ln ~he
pre~cnce o~ an acid cataly~t to produce hlgh oct~ne branched
chaln hydrocarbons (alXylate) Sor u~e in aviatlon gasollne
and motoi ~uel. Sp~clrlcally~ the olefin i8 comblned wit~
: 15 lsobutar.e in the pre~ence o~ an acld catalyst ln a reactor
and undQrgoes an cxoth~rmic r~action. The acid i~ then
separated ~rom the reactor ef~luent. Arter acid separatlon
the reactor e~luent then proceed~ to a serles o~ distlllatlon
column~ to separate the inert alkanes, the unreacted l~obutane
rOr recycle, ~md to recover the alkylate. Treating 18 al~o
perrormed on ~ome o~ the e~rluent to remove resldual acld
and undesired reac~lon products. A varlatlon of thl~
--1--
.' ~ ~,
,
. , . .
..
la~s~l
process has been to use the vaporization of a portion of the
reactor effluent to cool the reactor, see Hydrocarbon Processing,
September, 1974, page 206.
There are several disadvantages with the present art alkyla-
tion process. First, large amounts of coolant, usually water or
air, are necessary to condense the overhead streams from the dis-
tillation columns. Second, only a part of the reactor effluent
is vaporized when cooling the reactor. This vapor is recovered
as isobutane for recycle. The remaining liquid containing
alkylate and a large amount of isobutane must then undergo
treating to remove contaminants such as residue acid and then
be distilled to separate the isobutane and alkylate. The larger
this stream the larger the deisobutanizer column must be, and the
more heat that is necessary to effect separation. The present
invention reduces or eliminates these disadvantages while also
making a substantial reduction in the energy required for the
process.
In accordance with the present teachings, a process is
provided for catalytic alkylation of isobutane with an olefin
which comprises the steps of:
a) contacting the olefin with a molar excess of isobutane
and inert alkanes in the presence of an acid catalyst in a re-
actor to form a reactor effluent containing alkylate, isobutane,
acid catalyst and inert alkanes;
b) separating the acid catalyst from the reactor effluent
to form a separator effluent;
c) effecting a liguid vapor separation on the separator
effluent to obtain a liquid bottoms stream containing isobutane
and alkylate and an overhead vapor stream containing isobutane
and inert alkanes;
--2--
t,
~,.~:i
109~581
d) distilling the liquid bottoms stream to separate alkylate
product as a liquid bottoms product and isobutane as a vaporous
distillation effluent;
e) passing a portion of the separator effluent prior to the
liquid vapor separation step, as a cooling effluent in indirect
heat exchange with the vaporous distillation effluent to condense
isobutane thereln and to vaporize a portion of the cooling effluent;
and thereafter
f) effecting the liquid vapor separation step on the cooling
effluent.
In other words, the present invention relates to an
improved continuous process for producing alkylate in which
olefin and a molar excess of isobutane are reacted together
in an alkylation zone in the presence of an acid to form a
liquid effluent, the liquid effluent is removed from the
alkylation zone, and liquid effluent so removed is subjected
to processing to recover alkylate therefrom, the processing
including vaporizing at least a portion of the liquid effluent
to form vapors and thereafter condensing the vapors by cooling,
the improvement in accordance with the present invention compris-
ing cooling the vapors to be condensed b~ passing liquid effluent
from-the alkylation zone in indirect heat exchange with the
vapors.
.~
0 ; .
1094St~l (4~a8A)
Usln~ the present inventlon, the ~mount of lsobutane
that must be treated and reco~ered in the dlstlllatlon
column 18 greatly reduced, coollng ~ater $~ no longer necessary
for the dlstlllation column o~erhead conden~er, and the
variou~ distillatlon column~ may be operated at substantlally
lower pressures, enhanclng the separatlon process.
The central reature Or the lnventlon 1~ the use Or
the reactor e~luent to pro~lde coollng to condenser~ ln the
alkylation procc~s. By utllizlng the effluent ln thls
~snner~ sub~tantlal saYlng~ ln operatlng expenses are
reallzed~ along wlth savlngs ln capltal lnvestment ~or ne~
u~lt8 .
~ The lnventlon 1~ best underRtood by reference to
the drawlngs.
1~ DESC~IPTION OF THE DRAWINaS
Figure 1 sho~s a ~lmpll~led block dlagram Or the
lnventlon.
Flgure 2 shows the alkylatlon proces~ Or the
present lnventlon ln greater detall~
Flgur~ 3, whlch 1~ slmllar to Flgure 2, shows an
embodlment Or the lnvention whereln pressure-reduclng
Yal~es ar~ used on the reactor e~fluent and a ~aporous n-
butane dr~w i8 remoYed from the delsobutanlzer column.
~lgure 4 shows ln greater detail a ~apor sy~tem
wh~h may b~ used as the vapor 8y8tem lllu~trated in block
in Flgur~ 2.
~ lgure 5 3how~ stlll another embodiment Or the
present lnYention in accordanee wlth whlch the lnventive
4~
(4&8~ A)
proces~ i~ practicea ln conJunction with an alkylation
l~eaetOr producing ~oth a liquld errluent and a vaporou~
errluellt .
~ ererring to ~gure 1, olerln and lsobutane ~eed
enter a reac~or w.lich cont~lns tlle acid catalyst. The
strea~il leavin~ trle reac~or contaills acid cataly3t, alkylate,
lsobutane an~ lnert alkane~. ~i.is strea~ is then 3ent to an
Acid ~eparator, where the aci~ cat~lyst is separated from
the hyarocar~on mi~ture anà returned ~o tlle ~eactor. 'ilne
resultin~ ~-y~rocarbon 3nixture i5 then sent to one or more
~ondellsers to supply necessary coolln~. The use of this
y~rocar~on n~ixture rOr cooling tne condensers is the
in~ention. l'lle ef~luent from the Condensers then ~oes to
tlle Vapor-Liquia Separator where isobutane ~s partially
recovered as a va~or. ~y proc~3sing not ~howll in the drawing
thls vapor is compressed, conderlsed an~ returned to the
Reactor. r ~e liquid fro~ the Se~arator then continues to
the ~eisobutanizer Column where isobutalle i~ distilled
over~lea~ for recycle, ana alkylate product is recovered as a
bottoMs stream.
- ~eferring to tAe .nore detalle~ Fi~ure 2, olefin
and isobutane are comblned in line 101 and fed to a reactor
103 where the reactants are r~ixea wlth acid catalyst and
reacted to for~ll alkylate. qlhe product leave~ the reactor
throu~h llne 1~5 to the acld separator 107. Here the acid
i~ ~eparate~ ~rom the hydrocarbon mixture and returned to
the reactor through line 108. The hydrocarbon mlxture
containlng alkylate, isobutane and lnert alkanes leaves the
acld separator throug~ line 109.
The hydrocarbon m~xture goea to provide cooling ln
--5--
lO.!t~S~
(48~8 A)
the condensers throu~h lines 111 anli 112. ~eciflcally
r~ferrinO to line 111~ it is seen how the present inventlon
ls applied to the deisobutanizer column~ drocarbon
mlxture is transrilitted through line 11l to condenser 115
where at least part o~ tl~e hydrocarbor~ ixture i5 vaporized
to provide coolin~ in tne condenser. T.he hydrocarbon mlxture
arter providing cooling is transr~littéd throu~h line 116 to
the vapor-liquid separator 117. In the same manner coollng
is supplled to other conden~ers such 2S other column condensers
and compressor effluent condensers by taklng the hydrocarbon
mixture throu~h llne 11~, vapori~ng at least part of the
hydrocarbon mi~ture ln the condenser and transmittlng the
condenser effluellt through line 11l~ to the vapor-llquld
separator 117. In like manner t~e hydrocarbon mlxture is
used to cool th~ reactor through line 110 J an~ is then
- - transmltted throug~. line 113 to the vapor llquld se~arator.
In the vapor-liqul~ separator 117 a vapor-llquld
Aeparatlon takes place. The vapor contalns prlmarlly
lsobutane an~ inert alkanes~ and the llquld contalns isobutane
and aikylates. The vapors are transmltted throu~h line 118
where the vapor ls compressed and condensed in a va~or
system 119. .iormally ln the vapor syste~, 119 one or more
columns are employed to remove the lnert alkanes, such as
- propanes, from the lsobutane. ~he lso~utane stream is then
sent through line 120 to a second vapor-llquid separator
121. The liqui~ iso~utane stream i~ returned to the reactor
t~roug~ line 122 ~na the vapor ls returne~ to the vapor
system through line 118.
The liquld ~rom the ~irst vapor-llquid separator
lO!~ ~S81
(4888 A)
117 containlng lsobutane and alkylate then proceeds throu~h
line 123 to the treatlng sectlon 125 where re~idue acid and
acidlc compounds lrl the hydrocarbon mlxture are removed.
After treating, the llquid 18 tran~mitted throu~h llne 129
to the del~obutanizer column 131. Heat ls applled to the
column throu~h llne 133. Isobutane iq dlstllled and exlts
the top Or the colu~n as a vapor ln llne 135. Thl~ vapor ls
condensed in the overhead condenser 115 and the condensed
lsobutane 1~ then 8pllt ror rerlux to the column, and as
recycle to the reactor through llne 137. The alkylate
product la recovered 28 a llquid bottoms stream through line
139.
Figure 3, being slmllar to ~lgure 2, shows another
embodlment of the invention. The hydrocarbon mixture contaln-
15 lng alkylate, lsobutane and lnert alkPnes leaves the acldseparator 107 throu~h llne 109. The hydrocarbon mlxture
then goes to provlde coollng ln the condensers throu~h lines
111 and 112. Referring to line 111, a pressure reduclng
valve 141 18 located in front of column condenser 115. Thls
valve malntalns the hydrocarbon mlxture in llne 111 as a
liquid state. It al30 allo~s the downstream pressure o~ the
hydrocarbon mlxture golng lnto condenser 115 and e~lting ln
llne 116 to be reduced. The pressure i~ reduced surric~ently
to permlt vaporlzatlon of the hydrocarbon mlxture ln condenser
115. Some vaporizatlon may occur between valve 141 and
conaenser 115.- A slmllar valve 140 18 shown reduclng the
pressure of the hydrocarbon mixture ln line 110 whlch
provldes coollng to reactor 103. Other pressure-reduclng
valves (not ~hown) may also be found ln llne 112 going to
other condenser~.
10~4s~l
(4~88 A)
~ ure 3 also shows tile dcl~o~utanlzer column 131
havlng a vaporous ~laestrealrl draw 142. Normal butane may be
with~r~wn froF this column as a vapor ln llne 142 and
condense~ ln colu~n conden~er 143. Typlcally, coolant i8
useà ln llne 144 to provlde coollng to condenser 143.
However~ the hyàrocarbon mlxture Or llne 112 wlth a suitable
pressurereducing valve may also be used to provlde this
coollng. A n-butane sidestream draw may ~e used in the other
embodiments Or the present invention as well as the embodlment
speciflcally illustrated ln Figure 3.
~ lgure 4 shows a vapor sy3tem which may be employed
as vapor sy~tem 119 in the apparatus of Figure 2. The
hydrocarbon mlxture arter ~elng used as a coolant 1~ transmitted
through llne 113 to vapor-llquld separator 117 wherein a
vapor-llquid ~eparatlon takes place. The vapors are transmltte~
through line 118 to compressor 145. l'he vapors are then
compressed in the compre~sor and exit through line 146 to
the compres~or effluent coldenser 147. Coollng 13 provlded
througn line 148 to condenser 147 to condense the compressed
vapor effluent. Tl~e coollng ~leans ~,ay be coollng water but
ln another embo~imerlt of the lnvention the hydrocarbon
m~xture o~ 112 wlti~ a suitable pressure reduclng val~e may
al80 be used. The col~pressed condensed vapor efrluent exlts
the ~ondenser through llne 149. A portion of thls co~pressed
2j condensed errluent is taken through-line 150 to distillation
~olumn 152. The remalnder i~ transmitted through llne 151
to a secona vapor-llquid separator 121, as also shown in
Figure 2.
ri'ypically, di~tlllation column 152 is a deprvpanlzer
1094S81
column. Heat is applied to the column through line 153. Propane
is distilled and exits the top of the column as a vapor in line
154. This vapor is condensed in the overhead condenser 155. In
an embodiment of the invention, the hydrocarbon mixture of line
112, after pressure reduction is used to provide cooling to this
condenser. The hydrocarbon mixture after providing cooling is
transmitted through line 114 to the vapor-liquid separator 117
as shown in Figure 2.
The condensed propane from condenser 155 is then split
for reflux to the column through line 156 and also removed as a
product through line 157. The bottoms product of this column
containing mostly isobutane is transmitted through line 158 to
the vapor-liquid separator 121.
Still another embodiment of the present invention is
illustrated in Figure 5. In this embodiment, the alkylation
reaction is accomplished in such a way that a vaporous effluent
as well as a liquid effluent are produced by the alkylation
reactor. Such processes are well-known as illustrated, for
example, in U.S. 3,187,066 to Nathan, which was reissue as
20 Re.26,060.
As illustrated in Figure 5, feed is passed into reactor
172 from conduit 174 where the alkylation reaction takes place.
The vaporous reaction effluent produced is withdrawn from reactor
172 via conduit 176 and passed to a conventional vapor system 178
for the recovery of isobutane. Liquid reaction effluent exits
reactor 172 via conduit 180 and passes through condenser 182
where it partially vaporizes. The partially vaporized liquid
reactor effluent then passes through conduit 184 to vapor liquid
separator 186 where
10~4~1 ( 4888 A)
vapor and liquld are separated from one another. Separated
vapor travels v~a condult 188 to vapor system 178 where lt
ls proce~sed along wlth the vaporous reactor erfluent
produced ln reactor 172. The liquld stream pas~ing out o~
vapor ~iquld separator 186 travels vla conduit 190 to
deiosobutanlzer 192 where it ls separated. Alkylate product
ls recovered from delsobutanizer 192 via conduit 194 as
column bottoms whlle isobutane-rlch vapors are taken orf
delsobutanizer column 192 by means o~ conduit 196. I~obutane-
rlch vapors in conduit 196 pass through condenser 182 where
they pass ln lndlrect heat exch~nge relatlon with llquld
reactor effluent obtained from reactor 172. Becau~e o~ the
coollng effect created by the vaporlzation o~ llquld reactor
ef~luent in con~en~er 182, the lsobutane-rich vapors ln
condenser 182 condense to an lsobutane-rlch liquld stream.
A portlon Or thls lsobutane-rlch llquld stream ls sent to
re~lux vla conduit 198 whereas the remainer is recycled to
- reactor 172 via conduit 200.- Condensed lsobutane recovered
from vapor system 178 ls also recycled to reactor 17? via
20 condult 202 as 111ustrated.
As appreclated by those skllled in the art~ vapor
system 17~ normally includes a compressor ror ~acllltatlng
condensatlon Or the vapor passed thereto. In accordance
with the present lnventlon, thl8 compressor may lr desired
be a multl-stage compressor, and moreover the vapor red ~rom
vapor/liquld separator 186 or ~lmilarly vapor-llquld separator
-121 Or Flg. 2 to thls compressor may also be red to the
second or qubsequent stage~ rather than the rlrst stage o~
thl~ compre 80r.
The advantages o~ the present lnvention are manl~old.
--10--
(4888 A)
10945~31
Fir~t, because the ~eed to the deisobutanizer i3 reduced,
the volume of the stream treated 1~ reduced. Typlcally
this treating consl9t9 of a caustlc wash followed by a water
wash. The size Or the caustic treater is decreased effecting
a savlngs ln capital cost for the equipment requlred. A
second advantage is the size of the aeisobutanizer column.
Because a larger amount of isobutane is vaporized ln the
reactor effluent, less has to be recovered in the dlstillatlon
column. 5'his means a reduction in both the size of the
column and the heat input nece~sary for operatlon. Stlll
another advantage can be found by uslng the efrluent stream
as the coollng medium for the overhead condensers located on
the deisobutanizer and other distillation columns in the
process, sucr. as a depropa~ er and debutanizer. The use Or
; 15 the effluent stream allows lower operatin~ temperatures and
pressures for these colun~ls than could be reallzed u~lng
water or alr. Also, ellr~llnation of water as a coolant means
that the associated utllltles, such as a cooling tower, can
be decreased in slze or eliminated. 'i'hls reduction in
operatlng temperature and pressure of the columns ~erve~ to
lncrease the relative volatllity Or the key components,
meaning less energy lnput in the form o~ heat ls necessary
to perform the separation required. ~hus a unlque savings
i made in utllitles because tne water used to condense the
overhead i3 no longer neces~ary, and the heat to the tower
~or separatlon ls reduced.
-
(4a88 A)
PP~FhRR~D D~SCRIPTION OF ~M~ODIM~NT
In the pre~erred concept Or this lnventlon thereactor effluent, after acld ~eparatlon, is ~ent to the
overhead condenser~ on the distlllation columns ln the
process. Thls concept is preferred because lower temperature~
can be achleved uslng the reactor effluent than by uslng
coolin~ water. With lower temperatures and pressures ln the
column9 the separatlon proce~ is greatly enhanced. I~ more
than one condenser ls cooled by the effluent stream, they
may be connected in elther paràllel or serle~ rashlon. It
18 pre~erred that they be connected ln parallel to mlnlmlze
capltal C08t8.
Typlcally at least two dl~tillatlon columns are
pre~ent, a delsobutanlzer for separatlng l~obutane rrom the
alkylate product, and a depropanlzer to remove the li~hter
propane from the i~obutane. In 30me cases a third column
for separatlng butane from alkylate is also ~nvolved.
A varlant of thls lnvention 1~ to use the reactor
erfluent stream in other locations ln the process that
requlres coolln~, Thls may be ln addltlon to or exclusive
- o~ coollng the overhead condenser~ on the dlstillatlon
columns. Conden~ers are normally ~ound ln other locatlons om
alstlllation columns, such as coollng the llquld bottoms
product or condenElng a vapor slde~tream draw. For example,
ln3tead Or havlng a debutanlzer column, butane may be removed
~rom the process as a ~apor taken from some point in the
del~obutanlzer column. The reactor e~fluent may be used to
condense this vapor to produce a liquld butane product.
Another varlant 18 to use the reactor erfluent to
cool the ~ompressed vapor efrluent stream ~rom ths flrst
-12-
10945~1 ( 4888 A)
vapor-llquid ~eparator. These compressed vapors contalnlng
180butane and some inert alkanes must be condensed berore
they are ~ent to further dlstillatlon column~ to remove the
lnert al~anes or back to the reactor as recycle lsobutane.
The reactor effluent may be used ln the vapor compressor
effluent condenser, tnereby eliminating another u~age o~
coollng water.
It ls ant~clpated that this inventlon may be used
in any catalytic alkylatlon process involvlng an acld
catalyst. The acld catalysts that may be used are known ln
the art, lncludlng but not llmlted to sulfurlc and hydro~luorlc
acid. Pre~erred in the pre~ent lnvention ls the use of
~ul~uric acld cataly~t.
The reaction conditlon~ and parameters are unchanged
by thl8 lnventlon. I~ormally the reactor ~ 8 operated between
1-200 p~lg, and a temperature between -lO to 50C. The
olefln feed to the alkylatlon proces~ 1~ also known ln the
~i art~belng typlcally a hydrocarbon of 2-5 carbona and is not
affected by the ~resent inventlon. ~iormally the compositlon
Or the olefin ~eed depend~ on the specl~lc appllcatlon, but
may comprlse propylene, butylenes or amylene3. The olerln
reed may also contain varlous lnert alkanes, such as propane
and butane. The olefln 18 mlxed with lsobutane either
berore golng to the reactor or ln the reactor. Normally ~he
hlgher the ratio Or lsobutane to ole~in in the ~eed stock
the greater the yleld of alkylate. Thla external ratlo i8
u~u~lly ~bout 5:1 but can be 15:1 or higher. The pre~ent
ln~entio~ takes adYantage ~ thl~ ratlo by recoverlng
l~obutan~ ~or recycle ln a more ef~lclent and les~ costly
10~?45~'31
(4888 A)
nanner than the present art. ~y uslng thls lnvention in
existing units tllls ratio can be increased, thereby lmprovlng
tlle oc~ane Or the proauct witllout being limitea by the slze
of the delsobutanlzer.
As inalcatea above, the hy~rocarbon mixture belng
u~ea to provide coolin~ may be passed through a pre~sure-
reduclng valve prlor to its entry lnto the condensera lf
~eslred. The pressure 1~ reàuc~a sufflciently to permlt
vaporization and affect greater cooling in the condenser.
The pressure may be reauced to a pressure of 1 psia to about
50 p~ia. It is pre~erred to reduce thl~ pressure to 3 p81g
to about 5 psl~.
,
~P~CIFIC ~O~IM~hri'
~xample 1 and Co~;~arative ~xample A
1~ A com~uter slmulatlon was made Or an alkylation
proces~ as depicted ln the ~yarocarbon Processlng rererence
of September, 1974, page 206. Sulfurlc acld wa~ used a3 the
acid cataly3t. l'he reactant feea to both examples 18 glven
in Table I in barrels per ~tream day, being a cominatlon o~
lsobutane, butylene, and lnert alkanes.
TA~I~ I
~eactant Feed ~'o Alkylation Process
Isobutane 3830
~utylene 3090
Inert Alkane~ 1385
For comparlson, the amount Or product and lts
-14_
~0~? ~5~1
(4888 A)
ootane number of 98.5 wa~ held constant for both examples.
q'he isobutano ln the reactlon zone wa~ held at 80 p~rcent Or
the total ~eed plu8 recycle. ~ue to th¢ larger amounts Or
lnert alkanes ehat are recycled ln the e~rluent rerrlgeratlon
stream ln th~ pre~ent lnvention, thls has the e~rect Or
lncreaslng the lsobutane/olef~n ratlo in th~ reactor. ~he
other oper~tlng ~ondltions Or the reactor was the same ror
both examples.
ComparatlYe ~xample A show~ the present art. ~he
10 reactor erf'luent arter acld separatlon was used to cool the
reactor. A~ter coollng, the effluent stream was sent to the
rlrst vapor-liquld separator. The ll~uld from thls ~eparator
const~tuted the strea~ that was treated and sent as feed to
the d~lsobutani2er column. Cooling water was used as th~
coollng medlum ln the-oYerhead condenser o~ this column.
In ~xample 1, showing the pre~ent invention, the
reactor er~luent, ~n addition to cool~ng the reactor, wa~
sent ln a parallel manner to the overhead condenser of the
dei30butanizer. After coollng, the reactor efrluent ~ras
collected ln the rlrst vapor-llqu~ d separator. Table II
ohows th~ result~ Or these two e~amples. Quantitles ~hown
aro barr31~ per stream day.
10~4~
(4888 A)
rrA~L~ II
Com~arlson of Art Alkylatlon Wlth Invention
CoirlparatlveExam~le 1
r xample AInventlon
l . IC41n feed 3, ~3o 3, 830
2. IC4~1efin ratio
ln reactor 1~.9 18.2
3. IC4 ln vapor from
separator 25,945 52,594
4. Deisobutanlzer
IC4 in ~eed 26,~99 15,741
IC4 ln overhead
product 26,602 15, 344
condenser duty ~ 54.4 40.8
reboiler ~uty * ~3.o 47.2
column diameter (rt.) 11.3 9.8
l~M BTU/hr.
As shown ln Table II, rar more Or the isobutane
(IC4) contained ln the reactor effluent 19 vaporlzed, allowing
~or a more e~ficient recovery. The present lnventlon reduces
the amount of lsobutane ~eed to the delsobutanlzer by more
than 40 percent~ thereby reducing both the slze Or thls
col~mn and the utllitle~ required for dlst~llatlon.
ExamPle 2
Using the same feed composltion and reactor condltions
Or example 1, example 2 shows the efrect Or coollng the
overhead c9ndenser on the aeisobutanizer column wlth reactor
e~fluent only. Coolln~ water was completely ellmlnated, and
the refrigerant efrect Or the reactor er~luent allowed the
pre~sure ln the del30butanizer coluFn to be reduced rrom 15Q
p~ig to 17 psig. This reductlon in pre~sure lmprove~ separation,
and allowed the amount o~ heat needed ~or operatlon to be
reduced to 35.7 ~ TU/hr., more than 40 percent less heat
than was requlred ~or the present art ln Comparatlve Example
A.
-16-
