Note: Descriptions are shown in the official language in which they were submitted.
~3~9~
This invention relates to a process for regenera-
tying an alkaline stream containing mercaptan compounds.
A number of hydrocarbon streams produced by
refining operations or natural gas processing operations
contain mercaptan sulfur compounds and are commonly treated
to remove such mercaptan sulfur compounds in order to reduce
odor and/or corrosivity associated with these acidic
species. For example, alkyd and aureole mercaptans are
generally removed from such hydrocarbon streams by washing
10 or contacting such streams with an aqueous solution of an _
alkali metal hydroxide such as sodium hydroxide or
potassium hydroxide. The sulfur compounds are removed
into the alkaline stream as mercaptides, i.e. the metal
salts of the mercaptans. The alkaline solution containing
15 the mercaptides is then separated from the hydrocarbon
stream. In order for the overall treating scheme
described to be economically feasible, it is generally
necessary to regenerate the alkaline solution and to
recycle Kit for reuse in~contactlng more of the mercaptan-
2~0 containing hydrocarbon streams. By "regenerate" is month removal of most, if not all, of the mercaptides in the
alkaline stream, which mob accomplished by oxidizing
:
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I 'I
the mercaptides to disulfides. The disulfides, which are
relatively insoluble in the alkaline solution, may then be
removed therefrom as an organic layer. In order to carry
out the oxidation, a catalyst is generally employed. Any
S suitable catalyst known to those skilled in the art may be
utilized, including, for example, any of the catalysts
disclosed in US. Patent No. 3,574,093, such as cobalt
phthalocyanine or a derivative thereof, such as cobalt
phthalocyanine disulfonate.
A typical process for conventionally regenerating the
alkaline stream involves the use of an oxidation zone,
which typically involves a column having suitable
contacting means such as trays with bubble caps, or --
suitable packing material such as Raschig rings and the
lo like. The alkaline stream in the column is contacted with
air in the presence of the oxidation catalyst which is
generally contained in the alkaline stream to be
regenerated, in order to oxidize the mercaptides to
disulfides. Generally, such oxidation zones are
relatively large columns which are very expensive to
construct and maintain. After a spent alkaline marketed
containing stream ha been processed through an oxidation
zone, there is obtained a mixture of regenerated alkaline
solution and disulfides, which mixture is typically in the
form of a fine dispersion. This mixture must be
introduced into a settling zone wherein the mixture is
allowed to reside for a considerable time in order to
enable the dispersion to coalesce and separate into
layers. Due to the fineness of the dispersion, the
settler must be relatively large and occasionally
additional coalescing aids, mechanical and/or chemical,
may be required to insure separation of the disulfide and
alkaline phases. There are also systems where the
regenerated caustic disulfide mixture is contacted with a
35 solvent solution as is employed with other hydrocarbon
treating systems in order to effusively deal with this
separation problem.
....
I 5
Another conventional regeneration process consists of
air/steam stripping the mercaptides from the alkaline
stream, a process which also requires substantial
equipment and additionally is energy intensive.
As previously discussed, a settling tank is required
in conventional practice to process the dispersed
disulfide-c~ustic mixture by allowing the two phases to
coalesce and to separate. The problems of separating
constituents of a dispersed or emulsified mixture of this
nature necessitate equipment substantial in cost and size.
The overall removal of sulfur compounds from alkaline
streams thus is limited by several factors, including the
capacity of the equipment which is reflected in the
efficiency of the oxidation of mercaptides to disulfi~es
and the clearness or sharpness of the separation oath
resulting disulfide or disulfide/sol~ent mixture from the
caustic. Then, of course, there is the increased size of
equipment used in these processes with their attendant
higher installed cost and higher operating costs, which
are additional disadvantages.
It is conventional practice to treat various
hydrocarbon streams containing mercaptan sulfur compounds
by contacting such a stream with an alkaline solution such
as aqueous sodium hydroxide (caustic) whereby the
mercaptans are absorbed into the caustic and reacted with
it to form mercaptides and thus are separated from the
hydrocarbon stream. It is also conventional practice to
thereafter regenerate the marketed containing caustic
solutions to remove the mercaptides and thus render the
caustic solution suitable for reuse. The various methods
used to regenerate the caustic typically do so by
oxidizing the mercaptides to disulfides, generally in the
presence of an oxidation catalyst such as certain metal
chelates, including, for example, cobalt phthalocyanine
disulfonate. Such processes produce a mixture of
regenerated caustic and disulfides which must be separated
before the regenerated caustic can be reused. Typically,
I, .
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the oxidation of mercaptides to disulfides and the
separation of the regenerated caustic from the disulfides
is accomplished in separate steps. Also, the separation
is typically not complete, i.e. excessive disulfides
5 remain in the caustic solution and and regenerated caustic P
remains in thy disulfides. These shortcomings limit the
usefulness of the regenerated caustic for further -
extraction of sulfur compounds from the hydrocarbon stream
in question in that the entrained disulfides (sulfur
10 compounds) can be extracted back into the hydrocarbon
stream defeating the purpose of treating the hydrocarbon
stream with caustic, which is to remove sulfur compounds.
US. Patent No. 2,921,021, Urban, et at, relates to
the treatment of sour hydrocarbon distillate with an
15 alkaline solution. The spent alkaline solution containing
mercaptides is when mixed with air in a regenerator
whereby the mercaptides are oxidized to disulfides. The
regenerated caustic and disulfides are in the form of a
finely dispersed mixture. The dispersion is passed
20 through a coalescing system and then to a settling tank
whereby the disulfide compounds are separated from the
alkaline solution. Chile most of the disulfides are
removed in the settling tank, in some cases the settling
step may be followed by a naphtha wash to remove
I disulfides still retained in the alkaline solution.
US. Patent No. 2,853,432, Gleam, et at., discloses
the regeneration of used alkaline reagents by oxidizing
same using a phthalocyanine catalyst. For example,
mercaptides contained in a caustic solution were oxidized
30 to disulfides, which were then withdrawn from the
regeneration zone by skimming or by dissolving in a
suitable solvent such as naphtha.
Us. Patent No. 3,574,093, Strong, relates to a
multi-step process wherein the spent caustic generated by
35 treating a low-boiling hydrocarbon stream for mercaptan
removal is thereafter used in a second treating step
wherein a higher boiling sour distillate is sweetened. In
-5- ~23~7~3S
the sweetening step, the mercaptans in the spur distillate
are oxidized to disulfides. The disulfides exit the
treating stage in the hydrocarbon stream along with those
mercaptides which had been previously extracted from the
S low boiling hydrocarbon stream. Thus, the higher boiling
stream is sweetened and the partially spent alkaline
stream is regenerated at the same time. The regenerated
caustic is then introduced into a separation zone from
which the disulfide phase is recovered from the caustic
zone. The coalescence of the disulfide compound into a
separate phase is stated to be extremely difficult without
the use of coalescing agents. In addition, a high
residence time is used in the separation zone to further
facilitate this phase separation.
U. S . Patent No. 4, 362, 614, Asdigian, also relates to
a rnulti-st~p process for the extraction of mercaptans from
hydrocarbon streams with an alkaline solution, followed by
the regeneration of the mercaptide-containing alkaline
solution resulting from such extraction by oxidation in
the presence of a catalyst in an oxidation zone, followed
by the separation of the disulfides and the alkaline
solution by recantation within a phase separation zone.
From this process, the alkaline solution is recycled. In
addition to the requirement of a separate oxidation zone
and a large settling zone, the use of additional
coalescing means is said to be required.
US. Patent No. 3,758,404, Clouts; US. Patent No.
3,977,8~9, Clouts; and US. Patent No. 3,992,156, Clouts,
are directed to methods and apparatus for liquid-liquid --
mass transfer between immiscible liquids. A first liquid
is introduced onto the upstream surface portion of a
plurality of fixers extending generally along and secured
within a conduit. A second liquid, immiscible with said
: first liquid, is flowed through the conduit concurrently
with the first liquid, thereby dragging a film of the
first liquid along the fibers. The two liquids are
collected a the downstream end of toe conduit in a
6 34'7~
:"
collection vessel or gravity separator. my this technique,
a large surface area is generated between the two liquids
and mass transfer between the two liquids is facilitated.
As a result, a component of either of the liquids may be
transferred either into or out of the liquid film as it
moves along the fibers. The mass transfer may also occur
as the result of a chemical reaction at the interface -
between the liquids, such as the removal of acidic
constituents from a hydrocarbon by reaction with a base in
an aqueous solution, or the transfer may be without a
chemical reaction, such as by extraction from one liquid
to another. The patents teach the introduction of an
aqueous caustic solution onto the fibers and the flowing -
of gasoline containing acidic components concurrently
therewith. The acidic components of the gasoline react
with and are absorbed by the caustic.
The object of the present invention is to provide
an improved method of regenerating an alkaline stream such
as an aqueous caustic solution containing mercaptan sulfur
compounds, such as occurs in alkaline streams used in
removing mercaptans from hydrocarbon distillates.
The present invention provides a process for --
regenerating an aqueous stream of alkali metal hydroxide
containing marketed compounds, characterized by intro-
during an aqueous stream of alkali metal hydroxide containing
marketed compounds and an oxidation catalyst onto an
upstream end of a plurality of fibers positioned longitude-
natty within a conduit, a downstream end of the fibers
extending out of the conduit making contact with a
regenerated alkali metal hydroxide liquid in a collection
vessel; flowing a stream of hydrocarbon solvent having an
oxygen-containing gas dissolved therein concurrently through
the conduit, with and in contact with the stream of alkali
metal hydroxide, at a flow rate, temperature and pressure
whereby at least a portion of the marketed compounds in
the alkaline stream are oxidized to disulfides; extracting `~'
_ 7 _ ~-~3~7~5 --
.. ...
at least a portion or the disulfides into the hydrocarbon
solvent; receiving said hydrocarbon solvent and said alkali
metal hydroxide streams in a collection vessel wherein the
alkali metal hydroxide stream of reduced marketed content
S forms a layer in the lower portion of said collection
vessel and the hydrocarbon solvent containing the extracted :
disulfides forms a layer in the upper portion of said
collection vessel; withdrawing said hydrocarbon solvent
containing the extracted disulfide from the upper portion
of said collection vessel; and withdrawing the alkali metal
hydroxide of reduced marketed content from the lower
portion of said collection vessel for reuse.
The present invention results in an efficient
compact regeneration system for regenerating spent alkaline
solutions. Among its many advantages, other than those
mentioned above, entrainment of the alkaline solution in
the solvent/disulfide mixture is avoided since the method
of contacting the caustic with the oxygen required for
regeneration is not dispersive in nature. Yet another
advantage of the present invention is that of entrainment
of disulfide in the regenerated caustic is avoided. Thus,
separate washing steps to remove such entrained materials
are unnecessary. For all of the above reasons, less
equipment is required for the regeneration process of this
invention than with methods known to the art, and the
equipment which is utilized in the practice of the present
invention is smaller in size and simpler to operate than
that utilized in prior art processes. Therefore, equipment
investment and costs of operation are substantially lower.
In the drawings:
Fig. 1 is a schematic flow diagram of a process --
for regenerating an alkaline stream according to the
present invention.
The process of the instant invention makes use of a
mass transfer technique and apparatus as disclosed in V. S.
I.
I 7
Patent Nos. 3,977,829 and 3,~92,156, and reference may be
made to such patents for a full description of the mass
transfer apparatus.
In the preferred embodiment of the present invention
5 and with reference to Fig. 1, a mass transfer apparatus M us_
includes a bundle B of substantially continuous elongated
fibers mounted in a shroud S and contained within a
conduit 10. The conduit 10 has an outlet flange 10b that
is adapted for connection or placement with a mating
flange ha of collection vessel 11. A fluid distribution
means 12 is mounted within an upper position of conduit
inlet assembly aye for distributing the -
mercaptide-containing aqueous alkaline solution to be -
regenerated from the spent alkaline feed line 8 onto the --
fibers within the bundle B. A second solution line 14 is
attached to the conduit inlet assembly aye for delivering
the oxygen-containing solvent into the conduit inlet. The
conduit outlet 10b is attached to mounting flange ha of
the collection vessel if. Shroud S contains fiber bundle
B which extends partly within the confines of the
collection vessel 11. Other mechanical details of the
mass transfer apparatus M are not necessary to an
understanding of the invention and reference may be made --
to the aforementioned patents for further additional
mechanical details. The positioning of the downstream end
of the bundle B within the collection vessel if is such
that it is within the regenerated alkaline solution which
is collected as a lower layer in the collection vessel 11.
Collection vessel 11 contains a lower layer 18 of .
regenerated alkaline solution and an upper layer 20 of
hydrocarbon solvent containing disulfides. Collection
vessel 11 is preferably maintained at conditions which
avoid the separation of gases from the liquids therein.
The formation of gases within collection is avoided so as
to prevent entrainment of the hydrocarbon solvent
containing disulfides in the regenerated alkaline stream.
I
to
The fibers that comprise the bundle B art selected to
meet two criteria. The fiber material must be
preferentially wetted by the aqueous alkaline solution
introduced by feed line 8 and the fibers must be of a
material that will not contaminate the process or be
destroyed by it, such as by corrosion. Accordingly, --
inasmuch as the present invention deals with aqueous
alkaline solutions containing sulfur compounds, metallic
fibers and, in particular, stainless steel or special
corrosion resistant alloy fibers, are preferably employed.
The spent alkaline streams which may be regenerated
according to the present invention include, for example,
spent aqueous potassium hydroxide solutions and spent --
aqueous sodium hydroxide solutions, i.e. caustic. Such
alkaline solutions are widely used for treatment of a
variety of mercaptan containing hydrocarbon streams,
including liquid petroleum gas (LUG), butanes, butanes,
gasoline streams and naphthas and the like. These spent
alkaline solutions resulting from the treatment of the
aforementioned hydrocarbon streams can typically contain a
number of different mercaptan sulfur compounds, including,
for example, such mercaptans as methyl mercaptan, ethyl .`
mercaptan, n-propyl mercaptan, isopropyl mercaptan,
n-butyl mercaptan, and~hiophenol. Alkali metal sulfides
US can also be present in such spent alkaline solutions due
to the presence of hydrogen sulfide in the hydrocarbon
streams which were previously treated with the alkaline
solution. The presence of such sulfides does not
adversely affect the efficiency of the present invention.
In order to regenerate mercaptide-containing alkaline
streams according to the present invention, the spent
alkaline stream containing an oxidation catalyst is flowed
through line 8 into the inlet lo and to the fluid
distribution means 12 and onto the upstream end of the
US fiber bundle 6 as illustrated in Fig. 1. Simultaneously,
a suitable hydrocarbon solvent containing a dissolved -I
oxygen-con~aining gas such as air, is slowed through line
--10~
I
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14, into the conduit inlet loan and then concurrently with
and in intimate contact with the alkaline stream, passing
over the fibers of the fiber bundle B contained within
conduit 10, and then into the collection vessel 11.
5 During the time the two immiscible fluids are in contact --
within conduit 10, the mercaptides contained in the spent {.:
alkaline solution are oxidized to disulfides and the
disulfides are extracted into the hydrocarbon solvent and
are thus removed from the alkaline solution.
The oxidation reaction will occur at temperatures of
from ambient to about 150F. The preferred operating
temperature is from about 100F to about 130F.
The oxidation reaction is very fast, however, --
sufficient time must be allowed fox the oxygen to be
transferred to the alkaline stream and for the resulting
disulfides to be transferred back into the hydrocarbon
stream. Because of the efficiency of the mass transfer
apparatus, residence time in the fiber bundle may be
rather short, from about thirty second to about three
minutes. Preferred residence times are from about one to
about two minutes.
The oxidation catalyst contained in the alkaline
stream may be any suitable oxidation catalyst known to
those skilled in the art and preferably comprises a metal
phthalocyanine dissolved or suspended in the alkaline
stream entering the system through the line 8. Metal
phthalocyanines that may be employed include cobalt
phthalocyanine and vanadium phthalocyanine or sulfonated
or carboxylated derivatives thereof A preferred catalyst
comprises cobalt phthalocyanine disulfonate. The catalyst
concentration will vary depending in part on the level of
mercaptides in the alkaline stream, as will be understood
by those skilled in the art. Typically, the amount of
cobalt phthalocyanine disulfonate may range from about 10
to about 1,000 Pam by weight of the alkaline solution.
The oxygen required for the oxidation of the
mercaptides is introduced into the system through line 15
~3~7~
,
by dissolving oxygen or a oxygen containing gas, such as
air, in the hydrocarbon solvents stream 14. In the fiber
bundle B, the oxygen is transferred from the hydrocarbon
stream into the alkaline solution. Oxygen thus is
available for chemical reaction with the mercaptides in
the presence of ale oxidation catalyst contained in the
spent alkaline stream as the respective fluids move --
through the mass transfer apparatus M. The amount of
oxygen provided is at least equal to the stoichiometric
amount and generally is provided in excess of the
stoichiometric amount. The pressure in the system is
maintained at a level such that the desired amount of
oxygen can be dissolved into the hydrocarbon stream
without exceeding the volubility limits for oxygen ox the
oxyg~n-containing gas in the hydrocarbon.
The higher the marketed concentration of the spent
caustic to be regenerated, the more oxygen or oxygen
containing gas must be dissolved in the hydrocarbon and
higher system back pressure must be maintained in order to
jeep such amounts of oxygen containing gas in solution.
Typical system back pressures range from 10 prig to 100
prig with system back pressures of from about 25 prig to
about 75 prig typically being sufficient for most normal
marketed loadings. ...
Any suitable organic solvent which is immiscible with
the aqueous alkaline stream and does not otherwise
adversely affect the overall process may be utilized. For
example, many of the hydrocarbon streams described above
as being treatable for mercaptan removal with alkaline
30 streams may be employed as the solvent. Use of the -I
hydrocarbon which has been treated by the alkaline such as Jo
aromatics, gasoline, hexane, kerosene, nephew, or
mixtures of any such organic solvents will avoid the
possibility of contamination of the hydrocarbon stream by
solvent which is entrained in the recirculating alkaline
stream. ''
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The downstream end of shroud S containing the fiber
bundle B extends into the collection vessel 11
sufficiently so as to allow the end 16 of the fiber bundle
to contact the regenerated alkaline stream layer 18.
S Thus, as the alkaline and solvent streams flow from the
conduit 10 into the collection vessel 11, the regenerated
alkaline stream, being immiscible with the solvent,
separates and collects as a bottom layer 18 and the
hydrocarbon solvent, now containing disulfides,
accumulates as an upper layer 20 in the collection vessel
11. The interface 21 between the solvent and regenerated
alkaline solution may vary, but it is preferred that the
interface remain above the lower or downstream end of the
fiber bundle B as illustrated in Fig. 1. As a result of
lo the simultaneous oxidation of mercaptides to disulfides
and extraction of the disulfides into the solvent within
the fiber bundle B, a regenerated alkaline stream 17 of
reduced marketed content is produced.
The solvent and the regenerated alkaline streams are
withdrawn separately from the collection vessel 11. The
regenerated alkaline stream 17 is recycled for further
use, for example, in further contacting of
mercaptan-containing hydrocarbon streams. In a typical
regeneration system, it may be necessary from time to time
to purge some of the regenerated alkaline solution from
the recirculation loop and replace it with fresh alkaline
solution. This is generally done as needed to control the
buildup of sulfides or thiosulfates which may be present
in the system due to the presence of hydrogen sulfide in
the hydrocarbon stream being treated with the alkaline
solution prior to the regeneration step. The addition of
fresh alkaline solution may also ye necessitated due to
; the dilution effect resulting from the oxidation of the
mercaptides wherein water is a co-product of the oxidation
~35 reaction. by
The hydrocarbon vent containing disulfide
compounds may be processed further to recover the
-13- .
I
disulfide component therefrom, may be discarded in an
environmentally safe manner, or may be recycled to the
inlet line 14 for further use in the process of the
present invention. In the latter event, it may be
necessary to pass the solvent solution through debasing
zone 30 wherein the pressure is reduced by a suitable
pressure relief valve P to enable the dissolved gases
(generally rich in nitrogen if air is used as to oxygen
source since the major portion of the oxygen is consumed
in oxidizing mercaptides within the conduit 10) to come
out of solution and be separated therefrom through vent
31. This, of course, would not be necessary if oxygen --
itself were used for the oxidation. Also, since the -:
solvent loses its effectiveness as its level of disulfides
increases, it may be desirable to remove some of the
disulfide-containing solvents such as through line 19 and
to add fresh, lean solvent such as through line 23 from
time to time or in a continuous mode, in order to maintain
the proper efficiency of extraction of disulfides.
It has been found that the present method of
regenerating alkaline streams is quite superior to
conventional processes employing separate zones to effect
the oxidation and separation steps inherent in the overall
regeneration process. Moreover, the use of a suitable
fiber bundle contacting device in the present invention
provides for a compact process and results in reduced
capital costs.
It will be understood by those swilled in the art
that the efficiency of the overall regeneration process of
the present invention will depend upon a number of
paxameters, including the rates of mass transfer of oxygen
into the alkaline stream to provide the oxygen for the
catalytic oxidation of the marketed to disulfides and
the extraction of the resulting disulfide from the
35 alkaline stream into the solvent. Such parameters as the c.
surface area of the fiber bundle B, the rate of flow of
trim entering the lines 8 and I the amounts of
I
- 14 -
dissolved oxygen in either of the reactant streams, the
amount of catalyst contained in the alkaline stream,
residence time of the respective materials within the mass
transfer apparatus I and temperature and pressure
conditions may be varied depending on the chemical
composition of sulfur compounds contained in the alkaline -
stream to be regenerated, the type of hydrocarbon solvent
used, and other factors as will be appreciated by those
skilled in the art.
The following are examples illustrating the
process of the present invention and are not intended to
limit the scope thereof.
EXAMPLE 1
To demonstrate the effectiveness of carrying out
the process of the present invention, a bench scale mass
transfer apparatus was constructed embracing the principles
illustrated in U. S. Patent Jo. 3,977,829. The apparatus
consistent of a vertically oriented 4.57 m x 1.27 cm (16' x
1/2") I.D. beaded glass column (conduit) connected to a
horizontally oriented 0.91 m x 7.62 cm (3' x 3") I.D. beaded
lass pipe (collection vessel) with one-half inch beaded
glass nipples suitably located for removal of the lower
regenerated caustic layer and the upper solvent-disulfide
mixture. A fiber bundle consisting of stainless steel
fibers had been inserted within the beaded glass column
(conduit) such that the downstream end of the fibers would
; extend into the regenerated caustic layer in the lower
portion of the collection vessel.
As representative sample of the marketed-
containing alkaline solution to be subjected to the regenera-
lion process of thy present invention, a 15% by weight
aqueous solution of sodium hydroxide to which had been added
methyl mercaptan in an amount such that the marketed
concentration was 640~ expressed in Pam as sulfur was
introduced to the top of the fiber bundle at a flow rate
~23~ 35- ;
- 15 -
of 164 ml/min. The caustic solution also contained 100 Pam
of cobalt phthalocyanine disulfonate as an oxidation catalyst.
Also introduced into the top of the beaded glass column was
a kerosene solvent stream into which air had been injected
5 and dissolved. The kerosene flow rate was 602 ml/min. and I-
the air injection rate was 0.0096 SCUM. Lye caustic solution
and the kerosene solution flowed cocurrent~y through the
fiber bundle. The pressure in the system was maintained
at 2.655 kg/cm2 (52 prig) and the operating temperature
was approximately 56.1C (133F). In the collection vessel,
the regenerated caustic collected as a lower layer and the
kerosene collected as an upper layer, both of which were -
continuously removed, sampled and analyzed for mercaptan
sulfur content and disulfide content.
The regenerated caustic was found to contain
6 Pam as sulfur mercaptan sulfur and 2 Pam as sulfur,
disulfide. The kerosene solution obtained from the collection
vessel was found to have 5,240 Pam as sulfur, disulfide.
This data indicates that the regeneration of the caustic
solution was very effective and that the disulfide removal
in the kerosene solvent was very effective.
EXAMPLE 2
Utilizing the bench scale unit and procedures
described in Example 1, mercaptide-containing caustic
solution was prepared from 15% by weight solution hydroxide
to which ethyl Morton was added in an amount such that
the merited concentration was 428, expressed as Pam
sulfur. The caustic solution also contained 100 Pam of I-
cobalt phthaloeyanine disulfonate as an oxidation catalyst. --
30 This solution was introduced into the top of the fiber -
bundle at a flow rate of 170 ml/min. Also introduced into
the top of the beaded glass column was a hexane solvent
stream into which air had been injected and dissolved. The
hexane flow rate was 515 ml/min. and the air injection rate
was 0.007 SCUM. The pressure in the system was maintained
. ,-:
.,
I 5
- 16 -
at 3.51 kg/cm2 (50 prig) and the operating temperature was
approximately 41.1C (106F). The regenerated caustic was
analyzed and was found to contain nil mercaptan sulfur and
only 1 Pam as sulfur, disulfide. The effluent hexane was
analyzed and found to contain 1,700 Pam as sulfur, disulfide.
Again, the regeneration of the caustic was very effective :
both in terms of marketed sulfur and disulfide removal.
EXAMPLE 3
Utilizing the apparatus and procedures described in
Example 1, a synthesized spent caustic containing ethyl
marketed was regenerated by the process of the present
invention and the solvent employed was kerosene. Fifteen :
percent by weight sodium hydroxide was used to prepare the
spent caustic solution to be regenerated, the ethyl
marketed concentration was 1,230 Pam as sulfur, and the
caustic solution contained 100 Pam of cobalt phthalocyanine
disulfonate. This spent caustic was introduced into the
fiber bundle at a flow rate of 167 ml/min. The kerosene
flow rate was 600 ml/min. and the air injection rate
0.0068 SCUM. The pressure in the system was maintained
at 3.51 kg/cm2 (So prig) and the operating temperature
was approximately 41.1C (106F). The regenerated caustic
was found to contain nil mercaptan sulfur and only 6 Pam
as sulfur, disulfide. The effluent kerosene was found to
contain 5,2~0 Pam as sulfur, disulfide. This demonstrates
very effective regeneration of the caustic solution.
EXAMPLE 4
Utilizing the apparatus and procedures described
in Example 1, a synthesized spent caustic containing sodium `
thiophenate (an aromatic marketed) was regenerated by
the process of the present invention and the solvent employed
was hexane. Fifteen percent by weight sodium hydroxide was
used to prepare the spent caustic solution by adding
thiophenol in an amount such that the thiophenate concentra-
lion was 1,160 Pam as sulfur, and cobalt phthalocyanine
- 17 7~5- :
disulfonate was present at a concentration of 100 Pam. The
spent caustic was introduced into the fiber bundle at a
flow rate of 56 ml/min. The hexane flow rate was 305 ml/min.
and the air injection rate was 0.0062 SCUM. The pressure
in the system was maintained at 3.51 kg/cm2 (50 prig) and
the operating temperature was approximately 41.6~C (107F). --
The regenerated caustic was found to contain 190 Pam as
sulfur/ of thiophenate indicating substantial regeneration
of the caustic.
EXAMPLE 5
Utilizing the apparatus and procedures described
in Example 1, a sample of a spent caustic feed to a convent s
tonal caustic regeneration unit within a refinery was
subjected to the process of the present invention. The spent
caustic analyzed as follows:
Density 1.23 gtml
Percent Noah 21.9~
Sulfide 880 Pam
Mercaptides 2,260 Pam as S
Cobalt Phthalocyanine
Disulfonate 100 Pam
The approximate homology distribution of the mercaptides
was as follows:
Percentage
Homology f Total (as Sulfur)
Methyl 24
Ethyl 38
Isopropyl 11
N-Propyl 11
Sec-Butyl 4
Is Tert-Butyl 3
C5+ and Thiophenol g
The spent caustic was introduced into the top of the fiber
bundle at a flow rate of 43 ml/min. Kerosene was introduced ''
. , .
~2;~795
at a flow rate of 218 ml/min. and the air injection rate
was 0.0090 SCUM. The pressure in the system was maintained
at 3.51 kg/cm2 (50 prig) and the operating temperature was
approximately 31.1C (88F). The regenerated caustic was
found to contain nil thiophenate indicating that the
regeneration of the caustic was very effective. -
The present invention therefore, is well adapted -
to carry out the objects and attain the end and advantages
mentioned, as well as whose inherent herein. While
presently preferred embodiments of the invention have been
given for the purpose of disclosure, numerous changes in
the details ox construction, arrangements of parts and
operation of the process can be made which will readily
suggest themselves to those skilled in the art and which
are encompassed within the spirit of the invention ad the
scope of the appended claims.
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