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Патент USA US2404923

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July 30, 1946-
' R. J. PATTERSQN
2,404,923
ISOMERIZATION OF BÜTANE
Filed June 24, 1944
W7
Patented July 30, 1946
2,404,923
UNITED STATES PATENT OFFICE
2,404,923
ÍSOMERIZATION 0F BUTANE
Robert J. Patterson, Bartlesville, Okla., assigner
to Phillips Petroleum Company, a corporation
of Delaware
Application June 24, 1944, Serial No. 541,917
7 Claims. (Cl. 260--683.5)
2
1
This invention relates to the isomerization of
butane and more particularly to recovery of re
cycle hydrogen chloride of higher purity than
mol per cent of hydrogen chloride in the reaction
zone.
The principal object of the present invention
is to provide an improved process for the iso
heretofore.
Conventional practice in the isomerization of 5 merization of normal butane to isobutane. An
other object is to provide a process which enables
normal butane to isobutane involves passing the
vaporous butane in admixture with an appropri
ate amount of hydrogen chloride as a promoter
the recovery of a more pure hydrogen chloride
recycle stream in a simple and economical man
through a bed of aluminum chloride supported
on an absorbent carrier, preferably “Porocel,”
ner. Another object is to avoid the reduction in
yield attributable to the presence of isobutane in
withdrawing the vaporous eii‘luent, treating the
the hydrogen chloride recycle stream. Numerous
same as by scrubbing with concentrated sulfuric
acid to remove the volatilized aluminum chloride
other objects will more fully hereinafter appear.
therefrom, and passing the aluminum chloride
free etlluent into a unit for the separation of
hydrogen chloride for recycle. The separation 0f
hydrogen chloride is commonly ellected by pass
ing the vaporous eflluent after liquefaction into a
fractionating column operated as a stripper, the
The accompanying drawing portrays diagram
matically an arrangement of equipment suitable
for carrying out the present invention.
The present invention is directed to an im
provement in the process of isomerizing butane
which involves passing the vaporous normal bu
tane in admiXture with hydrogen chloride as a
feed usually being introduced near or at the top 20 promoter into contact with aluminum chloride
of the column.
In this column an overhead con- `
taining hydrogen chloride and lighter compo
nents and practically all of the propane together
with substantial amountsV of butanes is separated
as a catalyst under conditions such that isomer
ization of normal butane to isobutane is the prin
cipal reaction, withdrawing the vaporous reaction
eiiluent and passing it to a hydrogen chloride
g5
fractional
distillation zone and there separating
and recycled to the isomerization unit as a source
it into a vaporous overhead containing propane,
of hydrogen chloride. The bottoms product con
hydrogen chloride and lighter components and a
taining the balance of the butanes and ani7
bottoms fraction containing butanes and any
heavier components usually also together with
heavier
components. The improvement of the
some propane, is passed to a system for the sepa 30
present invention involves liquefying the vapor
ration of normal butane and isobutane in sub
ous overhead from the hydrogen chloride frac
stantially pure form for recycle and as product
respectively. The standard method of operating
is to operate the hydrogen chloride fractionator
tional distillation zone, passing the resulting
liquid into a second fractional distillation Zone
and there fractionally distilling it to separate it
into a vaporous overhead containing the hydro
large number of plates and under close control
gen chloride and lighter components and sub
is not necessary.
stantially free from propane and a bottom frac
Conventional practice as outlined above is not
tion containing substantially all of the propane
entirely satisfactory since the separation eiïected
and substantially free from hydrogen chloride.
in the hydrogen chloride fractionator is not clean. 40 The overhead from this second fractional distilla
Substantial amounts of isobutane and normal bu- '
tion zone is employed as recycle hydrogen chlo
tane are present in the recycle hydrogen chloride
ride, this stream being much richer in hydrogen
stream. objectionable amounts of propane are
chloride as a result of the Vfractionating referred
also present in the recycle hydrogen chloride
to. The bottoms from the second fractionation
stream and consequently the recycle stream is not 45 which is chiefly or substantially propane is re
as a stripper so that careful fractionation with a
desirably high in hydrogen chloride. These ob
jections are particularly disadvantageous where
it is being attempted to operate the isomerization
process at high hydrogen chloride levels, say over
cycled to the hydrogen chloride fractional dis
tillation zone as reflux therefor.
In the preferred practice of the present inven
tion the hydrogen chloride fractionator is oper
10 mol per cent and occasionally as high as 30 50 ated as a stripper thereby simplifying the sepa
2,404,923
‘a
u?
ration and allowing the stripper to be easily con
scrubbed in known manner with concentrated
sulfuric acid to remo-ve traces of aluminum chlo
trolled, all of the hydrogen chloride and propane
and some butanes going overhead as a result of
ride. The resulting scrubbed vapors after cooling
the rough separation. In this preferred embodi
ment this gaseous overhead is liqueiîed by com
pression and cooling and the resulting liquid is
pass via line S and pump l into hydrogen chloride
fractionator il which is generally operated as a
hydrogen chloride stripper in which case the feed
fractionated at the resulting pressure in the sec
ond fractional distillation zone. When the hy
drogen chloride fractionator is operated as a
enters at a point near the top of the column.
The overhead vapors from column i3 pass via line
â to compressor lo and cooler Il which serve to
liquefy them. The resulting liquid is passed at
stripper in this manner, it is necessary to com
press the stripper overhead to at least 400 pounds
the temperature and pressure imparted to it by
compressor Iii and cooler i l into fractionator l2
where separation is eifected between the hydrogen
feeding to the second fractional distillation. The
chloride and propane. The components lighter
second fractional distillation is conducted at the 15 than hydrogen chloride go overhead therewith.
per square inch and to cool it to not over 100° F.
in order to effect liquefaction and prepare it for
same elevated pressure. It is necessary to lower
the pressure on the recycle hydrogen chloride
stream to that prevailing in the isomerization
converter and likewise to lower the pressure on
the propane bottoms to the pressure prevailing
Any components heavier than propane appear in
the bottoms with the propane. The overhead
fraction is recycled to the isomerization unit via
line 23. Any excess, usually chiefly derived from
in the hydrogen chloride stripper before employ
ing the liquid propane bottoms from thD second
fractional distillation zone as reflux in the hy
drogen chloride stripper. ln a typical embodi
ment the gaseous overhead from the hydrogen ~
chloride stripper is compressed to 500 pounds per
square inch and cooled to not over 100o F.
By the introduction of liquid propane into the
top of the hydrogen chloride fractionator in ac
cordance with the present invention the hydrogen
chloride is removed overhead with propane vapors
and butanes are prevented from going overhead
and- are recovered in the kettle product. The in
coming isomerization eiiluent composed of normal
butano, isobutane, hydrogen chloride
some
propane and lighter components either in
vaporous or more usually in liquid form contacts
the liquid propane introduced at the top as re
the conversion of aluminum chloride to hydrogen
chloride in scrubber
may be Withdrawn from
the system via line ld. Pressure reducing valve
i5 is interposed in recycle line i3 for the purpose
of reducing the pressure on the recycle stream
from the high pressure maintained in column l2
to the `elatively low pressure maintained in
isomerization unit 3.
The liquid propane bottoms from column I2 is`
recycled via line it and pressure reducing valve
il into the top of HC1 stripper 8 and serves as
reflux therefor. Desirably this liquid propane is
reduced in pressure and expanded directly into
the top of column S thereby increasing the cool
ing cile-ct and increasing the extent of separation
between butanes and, lighter in column 3. if de
sired, for purposes of starting up or to make up
system losses, liquid propane from an ex
traneous source may be introduced Via line IB as
flux resulting in the vaporization of propane and
reflux for co-lumn ë.
condensation of butanes. The cooling effect of 49
riihe present invention has many advantages
the liquid propane may be further accentuated
over prior practice. Principal among them is that
by reducing the pressure of the liquid -propane
the hydrogen chloride recycle stream is kept much
bottoms from the second fractionator and eX
lower in propane content. Another advantage is
panding the liquid propane into the top of the
that presence of'butanes in the recycle stream is
hydrogen chloride fractionator in direct heat eX
completely prevented. The invention is especially
change
admixture with the materials therein.
advantageous over the use of a single precision
lìropane is formed in small amounts in the iso
high pressure hydrogen chloride fractionator
merization of normal butane to isobutane with
since in the present invention high pressure frac
hydrogen chloride and aluminum chloride.
tionation is restricted to the overhead only, frac
Usually the amount of propane formed ranges
tionator d commonly being operated at the con
from l to 2 mol per cent of the isomerization
ventional stripping pressure and with the con
effluent. Since my process effects continuous re
ventional degree of control. The injection> of
cycling of the propane derived from the hydro
liquid propane into the top of stripper 8 serves
gen chloride fractionator overhead, once the
to markedly cut down the amount of butanes go
process is in operation it is not necessary to in
ing overhead in line 9. The present invention is
troduce any propane from an outside source, the
particularly useful in isomeriïation processes
propane formed in the isomerization step being
where the hydrogen chloride concentrationin the
more than sufficient to make up for any system
losses. Any excess of propane will go out in the
bottom product of the hydrogen chloride frac
reaction zone runs as high as 25 to 30 mol per
cent. Numerous other advantages of the present
60 invention will be apparent to those skilled in the
tionator and will be removed in subsequent
art.
processing steps. In addition to the propane
Eramplc
formed in the isomerization reaction unit itself
by side reactions, a. small amount of propane is
Normal butane was isomerizee‘L to isobutane in
usually introduced with the normal butane feed
the conventional manner using vapor phase con
and is available together with the propane formed
version and a catalyst bed of “Porocel” impreg
in the reaction for the practice of the present
nated with aluminum chloride and the usual
amount of hydrogen chloride in the feed, the
invention.
In the drawing fresh normal butane feed after
pressure being 205-220 p. s. i. and the tempera
admixture with a suitable amount of hydrogen TO ture at the start being 240° F.
being gradually
chloride recycle ñowing in line 2 passes via line l
raised to 30 ° E'. as the converter remains on,-v
into isomerization reactor 3 where the conversion
stream in order to maintain conversion. The
takes place in a conventional manner. The
vaporous eñ‘luent after being scrubbed with con
vaporous isomerization eflluent passes via line 4
centrated sulfuric acid to remove AlClx was cooled
through sulfuric acid scrubber 5 Where it is
to effect liquefaction and pumped into a „hydro
2,404,923
5
6
gen chloride stripper operated at a pressure of
about 50 pounds above the pressure in the iso
merization chamber and sulfuric acid scrubber
and with a bottom temperature of 230° F. The
tion zone and employing same as liquid reflux
therefor.
2. In the process of isomerizing a butane to an
isomeric butane by passing a butane in admiXture
stripper overhead had the following composition, Ul with hydrogen chloride as a promoter into con
tact with aluminum chloride as a catalyst under
the figures being to the nearest one per cent:
conditions such that isomerization of a butane
Mol per cent
to an isomeric butane is the principal reaction,
Hydrogen _______________________________ __
9
some propane being formed by side reaction, and
Methane _______________________________ __
6
10 withdrawing a vaporous eli‘luent, the improvement
Ethane
___
__
8
which comprises cooling and condensing said va
Hydrogen chloride _______________________ __ 46
porous effluent, passing a resulting condensate to
Propane ________________________________ __ 30
a hydrogen chloride stripper and there stripping
Butanes ________________________________ __
1
a vaporous overhead fraction containing propane,
This overhead fraction was compressed to a pres
hydrogen chloride and lighter components from
sure of 500 p. s. i. and cooled to '70° F. and the re
a bottom fraction containing butanes and any
sulting liquid was passed to a iractionator hav
heavier components, liquefying said overhead by
ing 40 trays and operated at 500 p. s. i. and with
compressing and cooling, passing the resulting
liquid at the resulting pressure and temperature
a top temperature of 55° F'. The overhead from
into a fractional distillation Zone and there frac
this fractionator analyzed as follows:
tionally distilling it to separate it into a vaporous
Mol per cent
overhead` containing the hydrogen chloride and
Hydrogen
13
lighter components and substantially free from
Methane _______________________________ __
9
propane and a bottom fraction containing sub
Ethane _________________________________ __ 12
stantially all of the propane and substantially
Hydrogen chloride _______________________ __ 65
free from hydrogen chloride, recycling said last
Propane ________________________________ __
1
named overhead to the isomerization step as a
source of hydrogen chloride promoter, and re
cycling said last-named bottom fraction to the
Mol per cent
top of said hydrogen chloride stripper and em
Ethane and lighter _______________________ __ O
ploying same as liquid reflux therefor.
Hydrogen chloride _______________________ __
2
3. In the process of isomerizing normal butane
Propane ___________________________ _______ 95
to isobutane by passing a normal butane in ad
Butanes ____
___
3
mixture with hydrogen chloride as a promoter
into contact with aluminum chloride as a catalyst
35
The bottoms product was reduced in pressure to
under co-nditions such that isomerization of nor
the pressure of the hydrogen chloride stripper and
mal butane to isobutane is the principal reaction,
injected into the top thereof as liquid redux.
some propane being formed by side reaction, and
In carrying out the present invention the iso
The bottoms product had the following analysis:
merization is usually conducted :at pressures
ranging from 200 to 250 pounds per square inch
gage. rI‘he hydrogen chloride stripper is oper
ated at pressures ranging from 15 to 50 pounds
above the pressure prevailing in the isomeriza
»tion chamber or at pressures ranging from 215 .
to 300 pounds per square inch gage.
The second
fractionation step performed in fractionator l2
is carried out at pressures ranging from 400 to 600
pounds per square inch.
I claim:
1.. In the process of isomerizing a butane to
an isomeric butane by passing a butane in ad
mixture with hydrogen chloride as a promoter
into contact with aluminum chloride as a catalyst
under conditions such that isomerization of bu
tane to an isomeric butane is the principal reac
tion, and withdrawing a vaporous eliluent, the
improvement which comprises cooling and con
densing said vaporous efñuent, passing a resulting
condensate to a hydrogen chloride fractional dis
withdrawing a vaporous eiliuent, the improvement
which comprises cooling and condensing said va
porous effluent, passing a resulting condensate
to a hydrogen chloride stripper and there strip
ping a vaporous overhead fraction containing
propane, hydrogen chloride and lighter compo
nents from a bottom fraction containing butanes
and any heavier components, liqueíying said over
head by compressing to at least 400 pounds per
square inch gage and cooling to not over 100° F.,
passing a resulting liquid at the resulting pressure
and temperature into a fractional distillation zone
and there fractionally distilling it to separate it
into a vaporous overhead containing hydrogen
chloride and lighter components and substantially
free from propane and a bottom fraction contain
ing substantially all of the propane and substan
tially free from hydrogen chloride, recycling said
last-named overhead to the isomerization step
after reducing the pressure thereof to the pres
sure prevailing in the isomerization step, and
tillation zone and there separating it into a vapor 60 recycling said last-named bottom fraction to the
top of said hydrogen chloride stripper after low
ous overhead containing propane, hydrogen chlo
ering the pressure thereof to the pressure pre
ride and lighter components and a bottom frac
vailing
in said hydrogen chloride stripper and
tion containing butanes and any heavier com
employing same as liquid reflux therefor.
ponents, liquefying said overhead, passing the
4. In the process of isomerizing normal butane
resulting liquid into a fractional distillation zone 65
to isobutane by passing the normal butane in ad
and there fractionally distilling it to separate it
mixture with hydrogen chloride as a promoter
into a vaporous overhead containing the hydrogen
into contact with aluminum chloride as a catalyst
chloride and lighter components and substantially
under conditions such that isomerization of nor
free from propane and a bottom fraction contain
ing substantially all of the propane and substan 70 mal butane to isobutane is the principal reaction,
some propane being formed by side reaction, and
tially free from hydrogen chloride, recycling said
withdrawing a vaporous effluent, the improvement
last-named overhead to the isomerization step as
which comprises cooling and condensing said va
a source of hydrogen chloride promoter, and re
porous eiTluent, passing a resulting condensate to
cycling said last-named bottom fraction to the
top of said hydrogen chloride fractional distilla 75 a hydrogen chloride stripper and there stripping
2,404,923
7
8.
a vaporous overhead fraction containing propane,
lowering the pressureon said last-named'bottom
fraction to that‘prevailing in said >hydrogen chlo
ride stripper and expanding same in direct heat
exchange into the top of said stripper and em
ployingsame to provide reflux for said stripper.
6. The method of separating hydrogen chloride
from admixture with hydrocarbons comprising
butanes and propane, which comprises passing
hydrogen chloride and lighter components from
a bottom fraction containing butanes andi any
heavier components, liquefying said overhead by
compressing to at least 500 pounds per square
inch gage and'cooling to not over 100° FL, pass
ingthe resulting, liquid at the resulting pressure
and temperature into a fractional distillation zone`
said mixture to a hydrogen chloride stripper oper
and there fractionally distilling it to separate it
into a vaporous overhead containing the hydro 10 ated at a pressure of from 215 to 300 pounds
per square inch gage and there stripping a va
gen chloride and lighter components and sub
stantially free from propane and a bottom frac
porous overhead fraction containing propane,
hydrogen chloride and lighter components from
tion containing substantially all of the propane
a bottom fraction containing butanes and any
and substantially free from hydrogen chloride,
recycling said last-named overhead to the isom 15 heavier components, liquefying said overhead by
compressing to at least 400 pounds per square
erization step after lowering the pressure thereof
inch gage and cooling vto not over 100° F., passingv
to the pressure prevailing in the isomerization
the resulting liquid at the resulting pressure and
step, and recycling said last-named bottom frac
temperature into a fractional distillation zone
tion to the top of said hydrogen chloride stripper
after lowering the pressure thereof to the pres 20 and there fractionally distilling it to separate it
into a vaporous overhead containing the hydrogen
sure prevailing in the said hydrogen. chloride
chloride and lighter components and substan
stripper and employing same as liquid refluxA
tially free from propane and a bottom fraction
therefor.
containing substantially all of the propane and
5. In the process of isomerizing normal butane
substantially free from hydrogen chloride, low
to isobutane by passing the normal butane. in ad
ering the pressure on said last-named bottom
fraction to that prevailing in said hydrogen chlo
ride stripper and expanding same in direct heat
lyst under conditions such that isomerization of
exchange into the top of said stripper and em
normal butane to isobutane is the principal re
action, some propane being formed by side reac 30 ploying same to provide reflux for said stripper.
'7. The method of separating hydrogen chloride
tion, and withdrawing a vaporous eñluent, the
from admixture with hydrocarbons comprising
improvement Which comprises cooling and con
butanes and propane, which comprises passing
densing said vaporous eiiiuent, passing a resulting
condensate toa hydrogen chloride stripper oper
said mixture to a hydrogen chloride fractionalated at a pressure of from 215 to 300 pounds per 35 distillation zone and there separating it into av
vaporous overhead containing propane, hydrogen
square inch gage and there stripping a vaporous
chloride and lighter components and abottom
overhead fraction containing propane, hydrogen
chloride and lighter components from a bottom
fraction containing butanes and any heavier com
fraction containing butanes and any heavier
ponents, liquefying said overhead, passing the re
components, liquefying said overhead~ by com 40 sulting liquid into a fractional distillation zone
and there fractionally distilling it to separate it
pressing to at least L100 pounds per square inch
intoa vaporous overhead containing the hydro
gage and cooling to not over 100° F., passing the
resulting liquid at the resulting pressure and tem»
gen chloride and lighter components and substan
mixture with hydrogen chloride as a promoter
into contact with aluminum chloride as a cata
perature into a fractional distillation zone and
tially free fromv propane and a bottom fraction
there fractionally distilling it toseparate it into
free from propane and a bottom fraction con
'containing substantiallyv all of the propane. and
substantially free from hydrogen chloride, and
recycling said last-named bottom fraction to the
top of said hydrogen chloride fractional distilla
taining substantially all of the propane and sub
tion Zone and employing same as liquid reflux
a vaporous overhead containing thel hydrogen
chloride and lighter components and substantially
stantially free from hydrogen chloride, recycling 50. therefor.
said last-named overhead to the isomerization
step as a source of hydrogen: chloride promoter,
ROBERT J. PATTERSON.
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