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Patented Oct. 29, 1946
2,410,223
UNITED STATES PATENT orrics
2,410,223
TREATMENT OF HYDROCARBONS‘
Harold R. Legatski, Bartlesville, Okla, assignor
to Phillips Petroleum Company, a corporation
of Delaware
Application March 2, 1942, Serial No. 433,063
8 Claims. (01. 196-5)
1
2
,
This invention relates to the treatment of light
hydrocarbons for the removal of undesirable ‘com
ponents and more particularly it relates to the
treatment of such hydrocarbons as propane for
the removal of water, and hydrogen sul?de or
other undesirable and/or chemically reactive con
Another object of this invention is to provide a
method for the production of commercially pure
propane from a mixture, containing methane,
ethane, propane, water and hydrogen sul?de by a
stituents.
vide a method for the separation of propane from
a mixture containing methane, ethane, propane,
combined fractionation and chemical process.
Still another object of this invention is to pro
'
In the charging of alkylation, polymerization
and isomerization processes, it may be desirable
Water and hydrogen sul?de without having to
‘to use as nearly pure materials as economically 10 resort to an independent dehydration step fol
possible. Impurities commonly present in this
type of charge stock include such undesirables
lowing removal of the hydrogen sul?de.
Still other objects and advantages will be ap
as certain hydrocarbons, water or moisture and
parent to those skilled in the art by a careful
sulfur compounds, and in special cases still other
for such processes should be essentially free of
study of the following detailed disclosure.
Included in this speci?cation is the ?gure which
shows diagrammatically my apparatus and illus
moisture, hydrogen sul?de and mercaptans and
other hydrocarbons.
trates my method ofpproducing propane free of
water and hydrogen sul?de from a charge stock
compounds. For example, a butene charge stock .
containing propane and lighter paraf?nics,_mois
In one embodiment of this invention as herein
,
fully disclosed, I am describing a method for 20 ture and hydrogen sul?de.
In the operation of a propane fractionating and
the removal of moisture and hydrogen sul?de
dehydrating tower I have observed that the con
from a propane stock. It is known that dis
centration of hydrogen sul?de decreases very
solved water, hydrogen sul?de, methane and
rapidly on the plates immediately below the feed
ethane may be removed from propane by frac
plate and then decreases more slowly on toward
tionation. It is also known that it is generally.
the bottom of the tower. I propose to accom
more dif?cult to remove hydrogen sul?de than
plish the objects of this invention and to over
water or ethane to the speci?cation limits of
come the disadvantages of the above mentioned
commercial propane purity. In other words,
conventional methods by devising an operation
more fractionating plates or higher re?ux ratios
are required to remove hydrogen sul?de than are 30 .cyclebased upon my observation.
required to remove ethane and, in turn, ethane
requires more plates or reflux than does Water.
In order to produce dry hydrogen sul?de free
propane from a feed stock containing methane,
ethane, propane, hydrogen sul?de and dissolved ‘~
water, one of the following conventional methods
is ordinarily used: (1) Treat the entire feed with
caustic soda solution for hydrogen sul?de re
moval and subsequently fractionate out the water
which remains in solution in the hydrocarbon. 40
By this method the caustic soda consumption is
high, since all hydrogen sul?de must be removed
by this chemical action. (2) Produce a frac
tionator bottoms or kettle product containing
some hydrogen sul?de, then treat said bottoms
with caustic solution and redehydrate the hydro
gen sul?de Ifree hydrocarbon. By this method
the caustic soda consumption is low but an ad
ditional dehydration step isladded.
(3) By cut
ting more propane into the overhead product, it
is possible to fractionate both Water and hydrogen
sul?de out of the propane kettle product but this
method sacri?ces propane production in order to
remove hydrogen sul?de.
'
,
Bearing these conventional methods of opera
tion in mind one object of this invention is to
devise a method for separating commercially pure
propane from a gaseous mixture containing
methane, ethane,’ propane, hydrogen sul?de and
dissolved water. ;
7
Referring now to the ?gure, numeral i repre
sents a conventional fractionator, 2 and 3 con
ventional caustic washing towers, and this appa
ratus is equipped with heat exchangers, run
tanks, heaters and other auxiliary parts as ex
plained below.
In the operation of my process charge stock
containing methane, ethane, propane, hydrogen
sul?de and dissolved water enter the iractionator
I through feed line 4 at approximately the center
or mid-section of the tower. This charge stock
enters the said fractionator under sufficient pres
sure to maintain the charge in the liquid state
and to carry out fractionation. Heating element
5 furnishes heat for operation of the fractionator.
The tower overhead vapors pass out through line
6 and are cooled in condenser l, the liquid con
densate accumulating in re?ux accumulator 8
while the uncondensed gases exit through line 9.
The condensate required for re?uxing passes to
the tower through line It while that not thus
required leaves the system through line ll. Line
l2 conducts dry, and hydrogen sul?de free pro
pane from the fractionator to storage,-not shown,
Fractionation in tower I proceeds in a regular
manner with most of the propane produced from
the bottom of the iractionator or kettle as dry,
hydrogen sul?de free propane, and the other feed
components, that is, methane, ethane, water and
60 hydrogen sul?de plus some propane are produced
2,410,223
3
4
overhead from the fractionator. According to
my invention a portion of the descending liquid
is withdrawn from the tower a few trays below
the feed tray at a point where the hydrogen sul
?de content has been materially reduced. This
withdrawn liquid passes through line it‘, coolers
M, and lines 55 and into the lower portions of
the caustic washer towers 2 and 3. Bil-pass lines
It are provided so that either or both caustic
it may be concluded that the same may be ap
washers may be by-passed without disrupting
the operation of the fractionator.
so treated stream to the fractionator for subse~
The caustic washing towers 2 and 3 are pro
vided with caustic circulation pumps and lines
I‘! for the recycling or return of partially spent
caustic solution from the bottom of said con
tactors to the tops thereof. New caustic may be
added through lines it while spent caustic is re
moved from the contactors through outlet lines
l9. Caustic treated propane issues from the con
tactors through lines 29, passes through a com
mon header 2i into caustic settler Y22, and the
caustic free propane then leaves the settler
through line 23, is heated in exchanger It and
reenters the fractionator at a point immediately '
below its withdrawal point. Settled caustic solu
tion may be withdrawn from settler 22 through
draw-off 24.
As mentioned above, the hydrogen sul?de con
plied generally to the removal of water and a
chemically reactive material from a chemically
unreactive material, an example of which is the
production of a dry paraf?nic hydrocarbon from
a mixture containing water and unsaturated hy
drocarbons as impurities by removing a side
stream as herein shown and treating with sulfuric
acid to remove the unsaturates and returning the
quent dehydration by fractionation.
I claim:
1. In a fractionation process for the removal
of moisture and hydrogen sul?de from a low boil~
ing fraction of impure hydrocarbons the steps
comprising introducing the impure hydrocarbons
into a fractionating column intermediate the ends
thereof, removing overhead by fractionation
moisture and a portion of the hydrogen sul?de,
withdrawing at least a portion of the partially
puri?ed low boiling fraction from the fractiona
tor at a point slightly below the impure hydro
carbon introduction point, caustic treating said
withdrawn partially purified low boiling fraction
for removal of the hydrogen sul?de, substantially
separating said low boiling fraction from the
caustic, reintroducing the caustic treated portion
of the low boiling fraction ‘into the fractionator
at a point immediately below its withdrawal
taining hydrocarbon feed loses a large portion or
point
and a, substantial distance from the bottom
30
most of its hydrogen sul?de content on the plates
of the fractionator, and completing removal of
immediately below the 'fractionator feed plate,
the hydrogen sul?de and moisture by continued
fractionation, and removing the hydrogen sol?de free and dehydrated low boiling hydrocarbon
I remove a portion of the propane from the frac
fraction from the bottom portion of the frac
tionator at a point where most of the sul?de has - '
tionator.
already been removed by normal fractionation,
2. In a fractionation process for the removal
cooling said withdrawn propane, treating with
of moisture and an unsaturated hydrocarbon im
caustic solution for the substantially complete
purity from a low boiling para?inic fraction of
removal of hydrogen sul?de therefrom and pump
impure
hydrocarbons the steps comprising intro
40
ing the sulfur free stream back into the frac
ducing the impure hydrocarbons into a frac
tionator at a point just below its withdrawal
tionating column intermediate the ends thereof,
point but' high enough on the column to permit
removing overhead by fractionation moisture and
complete water and hydrogen sul?de removal be
a portion of the unsaturated hydrocarbon, with—
fore the propane is drawn off from‘ the kettle.
drawing at least a portion of the partially puri
The amount or proportion of the propane with
?ed parai?nic low boiling fraction from the frac
drawn for caustic washing is so determined that
tionator at a point slightly below the charge
when that amount of propane free of hydrogen
stock introduction point, sulfuric acid treating
sul?de is reintroduced into the fractionator, the
said withdrawn partially puri?ed para?‘inic low
amount of His remaining from the portion of
propane not caustic washed may be completely 50 boiling fraction for removal of the unsaturated
hydrocarbon, substantially separating said low
removed by fractionationby the time the recom—
boiling fraction from the acid, reintroducing this
bined propane reaches the draw-off of the frac
acid treated portion of paraf?nic low boiling frac
tionator, In addition, this operation is so ad~
tion into the fractionator at a point immediately
justed that the water carried in with the charge
stock and that added from the caustic Washing 55 below its withdrawal point and a substantial dis
tance from the bottom of the fractionator, and
operation are also completely removed so that
completing removal of the unsaturated hydrocar
only dry and hydrogen sul?de free propane may
bon and moisture by continued fractionation, and
‘be withdrawn as bottom product.
removing the puri?ed and dehydrated low boil
By removing the major part -of the-hydrogen
ing paraffinic hydrocarbon fraction from the bot~
sul?de by fractionation and therefore only a
tom portion of the fractionator.
relatively minor portion by caustic washing
3. In a fractionation process for the removal
greatly reduces the caustic costs. And, by re
of moisture and a chemically reactive impurity
moving by caustic washing at least a portion of
from a low-boiling fraction of impure hydro
the hydrogen sul?de which is normally difficult
to remove, permits operation of the fractionator 65 carbons the steps comprising introducing the
impure hydrocarbons into a fractionating col
at a much reduced re?ux ratio, and therefore
umn intermediate the ends thereof, removing
at a reduced cost of operation. My overall com
overhead by fractionation the moisture and a
bined process has been found to be easy to operate
portion of the chemically reactive impurity,
and to control,
While the embodiment fully ‘described has been 70 withdrawing at least a portion of the partially
puri?ed low-boiling hydrocarbon fraction from
directed to the removal of propane in a dry and
the fractionator at a point slightly below the
hydrogen sul?de free condition from a mixture
impure hydrocarbon introduction point, treat
containing methane, ethane, propane, dissolved
ing said withdrawn partially puri?ed low-boil?
water and hydrogen sul?de, it is obvious that the
ing hydrocarbon fraction with alchemical non
principles involved have a wider application, and
and below these plates the sulfur reduction is
appreciably lessened. According to my invention
5
6
reactive to said low-boiling hydrocarbon frac
at a point below the impure hydrocarbon intro
duction point, treating said withdrawn partially
tion for removal of the chemically reactive im
purity, substantially separating out said chemi
cal and reaction products, reintroducing this
puri?ed low-boiling hydrocarbon fraction with a
chemical non-reactive to said low-boiling hydro
carbon fraction for removal of the chemically re
active impurity, substantially separating out said
chemical and reaction products, reintroducing
chemically treated portion of low boiling hydro
carbon fraction into the fractionator at a point
immediately below its withdrawal point, and a
substantial distance from the bottom of the
fractionator and completing removal of the
this chemically treated portion of low-boiling hy
drocarbon fraction into the fractionator at a
point below its withdrawal point and a substan
tial distance from the bottom of the fractionator,
and completing removal of the chemically reac
chemically reactive impurity and moisture by
continual fractionation, and removing the puri
?ed and dehydrated hydrocarbon fraction from
the bottom portion of the fractionator.
tive impurity and moisture by continual fraction
4. In a fractionation process for the removal
ation, and removing the puri?ed and dehydrated
of moisture and hydrogen sul?de from a low 15 hydrocarbon fraction from the bottom portion of
boiling fraction of impure hydrocarbons the steps
the fractionator.
comprising introducing the impure hydrocar
bons into a fractionating column intermediate
the ends thereof, removing overhead by frac
tionation moisture and a portion of the hy
7. In a process for the fractionation of a mix
ture of two substances having different vapor
pressures, one of said two substances being a de
sired hydrocarbon product, the other of said two
drogen sul?de withdrawing at least a portion
substances being a chemically reactive impurity
of the partially puri?ed ‘low-boiling fraction
and said impurity being the more volatile of the
from the fractionator at a point below the
two substances, the combination comprising the
impure hydrocarbon introduction point, caustic
steps of introducing the mixture into a vertically
treating said withdrawn partially puri?ed low 25 disposed distillation column at an intermediate
boiling fraction for removal of the hydrogen sul
point, said column having an overhead vapor out
?de, substantially separating said low-boiling
let and a bottom liquid outlet, removing overhead
fraction from the caustic, reintroducing the cans
by fractionation at least a portion of said im
tic treated portion of the low-boiling fraction into
purity and partially purifying the mixture there
the fractionator at a point below its withdrawal 30 by, withdrawing at least a portion of said partial
point and a substantial distance from the bottom
ly puri?ed mixture from the fractionator at a
of the fractionator, and completing removal of
vpoint between said intermediate point and the
the hydrogen sul?de and moisture by continued
bottom outlet but relatively closer to said inter
20
fractionation, and removing the hydrogen sul?de
mediate point, substantially separating said im
free and dehydrated low-boiling hydrocarbon 35 purity from said partially puri?ed mixture there
fraction from the bottom portion of the frac
by further purifying the mixture, reintroducing
tionator.
5. In a fractionation process for the removal
of moisture and an unsaturated hydrocarbon im
said further puri?ed mixture into the fractiona
tor at a point intermediate said withdrawal point
and the bottom outlet but adjacent said with
purity from a low-boiling para?inic fraction of
drawal point, completing removal of the impurity
impure hydrocarbons the steps comprising in
by further fractionation, and removing said de
troducing the impure hydrocarbons into a frac
sired hydrocarbon product at said bottom outlet.
tionating column intermediate the ends thereof,
8. In a process for the fractionation of a mix
removing overhead by fractionation moisture and
ture of two substances having different vapor
a portion of the unsaturated hydrocarbon, With 45 pressures, one of said two substances being a
drawing at least a portion of the partially puri
desired hydrocarbon product, the other of said
?ed para?inic low-boiling fraction from the frac
two substances being a chemically reactive im
tionator at a point below the charge stock intro
purity and said impurity being the more volatile
duction point, sulfuric ‘acid treating said with
of the two substances, the combination compris
drawn partially puri?ed para?inic low-boiling 50 ing the steps of introducing the mixture into a
fraction for removal of the unsaturated hydro
vertically disposed distillation column at an in
carbon, substantially separating said low-boiling
termediate point, said column having an over
fraction from the acid, reintroducing this acid
head vapor outlet and a bottom liquid outlet, re
treated portion of para?inic low-boiling fraction
moving overhead by fractionation at least a por
into the fractionator at a point below its with 55 tion of said impurity and partially purifying the
mixture thereby, withdrawing at least a portion
drawal point and a substantial distance from the
of said partially puri?ed mixture from the frac
bottom of the fractionator, and completing re
moval of the unsaturated hydrocarbon and mois
tionator at a point between said intermediate
point and the bottom outlet but relatively closer
ture by continued fractionation, and removing
the puri?ed and dehydrated low-boiling paraf 60 to said intermediate point, contacting said with
?nic hydrocarbon fraction from the bottom por
drawn portion of‘ the partially puri?ed mixture
tion of the fractionator.
with a chemical treating agent for further re
6. In a fractionation process for the removal
moval of said impurity from the mixture, sepa
of moisture and a chemically reactive impurity
rating said further puri?ed material from the
from a low-boiling fraction of impure hydrocar 65 chemical treating agent and reintroducing this
bons the steps comprising introducingv the im
further purified material into the fractionator at
pure hydrocarbons into a fractionating column
a point intermediate said withdrawal point and
intermediate the ends thereof, removing overhead
the bottom outlet but adjacent said withdrawal
by fractionation the moisture and a portion of
point, completing removal of the impurity by
the chemically reactive impurity, withdrawing at 70 further fractionation, and removing said desired
least a portion of the partially puri?ed low-boil
hydrocarbon product at said bottom outlet.
ing hydrocarbon fraction from the fractionator
HAROLD R. LEGATSKI.
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