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Description  |
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FIELD OF THE INVENTION
This invention relates to novel liquid membrane formulations which are
water-in-oil emulsions wherein the oil phase comprises a sulfonated
polymer having a backbone which is substantially nonaromatic, for example,
less than 10 mole % aromatic, and uses thereof in high temperature liquid
membrane processes. The emulsions are useful in liquid membrane water
treating processes, especially in water treating processes which are
desirably run at high temperatures. In the most preferred embodiment,
these compositions are used in a liquid membrane sour water treating
process wherein a waste water stream containing ammonium sulfide is
contacted with a liquid membrane emulsion, i.e., the emulsions of the
instant invention, at conditions whereby ammonia permeates through the
external phase of the emulsion into an acidic internal phase wherein it is
converted to a nonpermeable from, e.g., ammonium ion, while H.sub.2 S is
continuously stripped out of the waste water solution by means of an inert
gas, e.g., steam. Processes of this sort are most effectively carried out
at temperatures greater than 80.degree.C. wherein the emulsions of the
instant invention have excellent stability.
DESCRIPTION OF THE PRIOR ART
In U.S. Ser. No. 382,466, filed July 25, 1973, in the names of N. N. Li and
R. P. Cahn, a process for removing the salt of a weak acid and a weak base
from solution by means of the liquid membrane technology disclosed in U.S.
Pat. Nos. 3,410,794, 3,617,546 and 3,779,907, all herein incorporated by
reference, is disclosed. The process disclosed in U.S. Ser. No. 382,466
utilizes the liquid membrane technology to remove either the weak acid or
weak base or their hydrolysis products from solution by permeating through
the external phase of the liquid membrane emulsion, and converting same
into a nonpermeable form in the interior phase. Simultaneously the weak
acid or weak base or hydrolysis product thereof may be stripped from
solution by means of an inert gas or alternatively by subjecting the
system to subatmospheric pressures. This process has been found to be most
effective when run at high temperatures, for example, 80.degree.C. It has
been found, however, that, at temperatures in this range, many liquid
membrane formulations, i.e., water-in-oil emulsions, are unstable. In the
process of this invention, this problem is solved by means of novel
formulations which have been found to be stable at temperatures up to
100.degree.C.
SUMMARY OF THE INSTANT INVENTION
The instant invention relates to novel liquid membrane formulations which
are water-in-oil emulsions wherein said oil phase comprises a sulfonated
polymer having a backbone which is substantially nonaromatic. These novel
compositions also comprise a solvent for said sulfonated polymer which is
immiscible with water, and although, not necessary, an oil-soluble
surfactant may also be used in the formulation. The aqueous interior phase
of these emulsions may comprise a base or an acid. The emulsions of this
invention are especially suitable for use in liquid membrane processes
wherein aqueous solutions are treated at high temperatures with liquid
membrane formulations. Furthermore, when these emulsions are being
utilized in the preferred process for treating sour water, the emulsions
will usually comprise either a strong acid or a regenerable acid. The
regenerable acids used in forming the compositions of the instant
invention are fully described in U.S. Ser. No. 382,466.
The liquid membrane formulations of the instant invention, as stated above,
will comprise a sulfonated polymer wherein the backbone of said sulfonated
polymer is substantially nonaromatic. In general, sulfonated polymers
which are useful in the compositions and process of the instant invention
are disclosed and claimed in U.S. Pat. No. 3,642,728 herein incorporated
by reference. The term "substantially nonaromatic in nature" means that
the backbone will comprise less than 25 mole %, preferably less than 10
mole % aromatic groups. This is a necessary limitation since it has been
found, unexpectedly, that aromatic-containing sulfonated polymers do not
form stable emulsions with the solvent systems utilized in certain higher
temperature liquid membrane processes, e.g., liquid membrane sour water
treating.
The preferred sulfonated polymers of the instant invention are selected
from the group consisting of sulfonated butyl polymers and sulfonated
ethylene-propylene copolymers. Most preferably, compositions of the
instant invention comprise a sulfonated butyl polymer. The butyl polymer
is prepared by copolymerizing isobutylene and isoprene, alteratively with
a third monomer, e.g., cyclopentadiene. The preferred sulfobutyl polymers
of the instant invention will contain from about 0.25 to 10 mole %
sulfonic acic groups, more preferably from about 0.5 to 5 mole % sulfonic
acid groups. This copolymer may be prepared by the methods described in
U.S. Pat. No. 3,642,728. The preferred sulfobutyl polymer of the instant
invention will have a number average molecular weight of at least 1,000,
preferably from 5,000 to 50,000.
Other sulfonated polymers which are operable in making the compositions of
the instant invention may be selected from the group consisting of
sulfonated copolymers of isobutylene and piperylene, isobutylene and
cyclopentadiene, isobutylene and methylcyclopentadiene, and isobutylene
and beta-pinene. The diene composition of these polymers may range from
0.5 to 30%, preferably 1 to 25 mole %. Various sulfonated terpolymers are
also useful in preparing the compositions of the instant invention. For
example, isobutylene may be copolymerized with any two of the above
conjugated dienes and the resulting copolymer sulfonated in accordance
with the teachings of U.S. Pat. No. 3,642,728 to yield sulfonated polymers
useful in the instant invention.
Other less preferred copolymers for use in the instant invention are
prepared by copolymerizing ethylene and propylene with a diene, e.g.,
dicyclopentadiene, ethylidene norbornene, or 1,6-hexadiene and sulfonating
the copolymer as described above. These terpolymers may have from 0.2 to
10 mole % unsaturation and more preferably from 0.5 to 7% prior to
sulfonation.
Finally, highly unsaturated nonaromatic polymers may be sulfonated and used
in preparing the compositions of the instant invention. For example,
polybutadiene and polyisoprene homopolymers may be so utilized.
The polymers described above, in general, will contain from 0.25 to 20 mole
% sulfonic acid groups, preferably from 0.5 to 5 mole % sulfonic acid
groups, and have a number average molecular weight of at least 1,000,
preferably from 5,000 to 50,000.
The use of emulsions prepared from sulfonated polymers is not restricted to
sour water treatment. They have a very wide utility in other liquid
membrane processes. In systems involving strong acids and/or bases, these
emulsions are particularly advantageous since the sulfonated polymers,
described above, act as emulsifying agents, and unlike many surfactants
are not prone to hydrolysis under the conditions of use.
In cases where high temperatures and strong acids or bases are used, it is
essential that solvent for the sulfonated polymer be selected judiciously.
Thus, solvents such as esters which can hydrolyze easily should not be
used. Another restriction is volatility of solvents. Thus, hydrocarbons
and other solvents which are volatile at 80.degree.C. or are steam
distillable cannot be used. Another criteria for selection of solvents in
water-treating processes is toxicity. Solvents which leave a toxic residue
in water must be avoided. It is also important that solvents used in this
process should be liquids under the operating conditions to provide liquid
membranes and should not have a tendency to solidify during use. The
solvent should also be selected so that the specific gravity of the
formulated emulsion differs from that of the feed stream, with which it is
to be contacted by at least 0.025, to allow easy separation of the
emulsion from the feed. Thus, if the difference between the specific
gravity of the feed stream and the emulsion is too small, the separation
thereof is a time-consuming process. Other considerations will be apparent
to those skilled in the art. For the reasons given above, the preferred
solvent will be chosen from the following group.
Petroleum distillates having a boiling point of >200.degree.C. Higher
boiling normal paraffins which have a melting point of 70.degree.C. or
more should not be used, unless they are mixed with other solvents to
lower their melting points. Paraffinic solvents, which may be lightly
substituted with halogens such as chlorine or benzene or cycloalkyl rings,
i.e., less than 10 mole %. Preferred solvents include the petroleum
distillates known as isoparaffins having an average carbon number of from
about 10 to about 100, most preferably from 30 to 75. Examples of solvents
of this type are the refined isoparaffins known as Solvent Neutral types,
available from Exxon Chemical Company. Almost all of these are suitable in
the instant invention, e.g., Solvent Neutral 100, Solvent Neutral 150,
Solvent Neutral 600 and the various grades inbetween. (The numeral refers
to the SUS viscosity at 100.degree.F.) Other petroleum fractions such as
bright stock, Coray 90 and the like are also suitable. These are petroleum
lubricating oils having viscosities of 479.4 and 412.2 centistokes,
respectively, at 100.degree.F. In many applications, it may also be
desirable to use mixed solvents such as, for example, Solvent Neutral 100
and Solvent Neutral 600, in combination.
The most preferred form of the sulfonated polymers used in preparing the
compositions of the instant invention is the free acids, although long
chain amines or polyamines can be used as neutralizing agents. The amines
useful as neutralizing agents include triamines, e.g., containing C.sub.6
to C.sub.16 hydrocarbyl radicals, such as, for example, trioctylamine; and
diamines, e.g., containing C.sub.8 to C.sub.16 hydrocarbyl radicals, such
as, for example, didodecylamine. The amines are selected on the basis of
their lack of solubility in water. If these amines or their salts have
appreciable solubility in water, they are likely to be lost when strong
acids and bases are utilized in the internal phase.
As will be described later, salts of these sulfonic acids such as ammonium,
potassium, sodium, etc., are not particularly useful in these applications
due to the lack of their solubility in the solvent system used.
The polymers containing free sulfonic acid groups are prepared by first
sulfonating the copolymers such as, for example, isobutylene-isoprene
copolymer as described in U.S. Pat. No. 3,642,728 and then replacing the
solvents used in their preparation such as methylene chloride, volatile
hydrocarbons and the methanol quenching agent by the solvent desirable for
emulsion formation, e.g., Solvent Neutral 100 or Solvent Neutral 600. This
process is known in the art as solvent replacement. Another method is to
neutralize the salts of these sulfonic acid polymers with an acid, e.g.,
sulfuric acid, and extract the polymer with the desired solvent. Solutions
of these polymers when stored in amber-colored bottles are indefinitely
stable. The concentration of the sulfonic acid polymers used in preparing
the compositions of the instant invention may vary from 0.05 to 40 wt. %,
preferably from 0.1 to 30 wt. %, in the solvent.
In many liquid membrane processes, such as sour water treatment, it is
desirable to maximize rate of ammonia transfer to internal phase as well
as the removal of H.sub.2 S by the inert gas, e.g., steam, or by
subatmospheric pressures. This is accomplished by carrying out the process
at temperatures higher than ambient wherein the vapor pressure of H.sub.2
S increases substantially and its solubility in water is decreased. Thus,
at 25.degree.C. the solubility of H.sub.2 S in water at 25.degree. is
0.34% and at 90.degree.C. it is 0.04%. It is evident that when running
this process at atmospheric pressure, a temperature of 80.degree. to
85.degree.C. would be very practical.
In various liquid membrane processes such as sour water treatment, it is
desirable to use strong acids or bases in the internal phase of the
emulsion. Unfortunately, with the increase in temperatures, the hydrolysis
rate of commonly used surfactants, such as Span 80, an oleic acid ester
increases drastically. Thus, many surfactants are generally unsuitable for
use at these higher temperatures when strong acids or bases are present.
One of the outstanding advantages in using the sulfonic acid polymers
described above is that no additional surfactant is needed to stabilize
the emulsion, thus, risk of hydrolysis and/or decomposition at higher
operating temperatures is avoided. The sulfonated polymers provide both
additive and surfactant properties needed in the liquid membrane
processes, and are not subject to the above-described disadvantages of the
commonly used surfactants. Also, the sulfonic acid polymers possess the
proper hydrophiliclipophilic balance at the operating temperatures, e.g.,
temperatures of from 80.degree. to 100.degree.C. It has been noted that
unlike many other additives, e.g., polyisobutylsuccinic
anhydridetetraethylenepentaamine, commonly used at the operating
temperatures described above, the sulfonic acid polymers are inert to
hydrogen sulfide attack, in liquid membrane processes.
All of the above factors make the sulfonic acid polymers described above
particularly suitable for forming emulsions, useful in high temperature
liquid membrane processes especially liquid membrane sour water treating
processes.
The above components, that is sulfonated polymer, solvent with or without a
surfactant, are selected with consideration of their interaction to form
emulsions which are stable at high temperatures and especially in the
presence of strong acids and bases. The choice of specific combinations is
within the skill of the artisan in the field of emulsion technology with
the teaching of this disclosure before him. In general, the emulsions of
the instant invention are prepared by techniques known in the art. For
example, the sulfonated polymer may be dissolved in the solvent followed
by the addition and dissolution of the surfactant. However, the components
can be combined in any order. The aqueous internal phase may then be added
to the oil phase while agitating with any of the devices known in the art
for preparing stable emulsions. For example, paddles with a stirrer
operable at high speeds may be used to emulsify the components.
Other well-known emulsion-forming techniques which may be utilized include
the use of colloid mills in which large droplets are broken up by the
intense shearing forces. Homogenizers can also be used after a preliminary
emulsification in a mixing vessel, colloid mill, or other device. In this
type of operation, the coarse emulsion is pumped at a high velocity
through the annular opening of a valve. The droplets are disrupted, partly
by the simple "sieving action" and partly by the intense shearing forces
which are set up in the annulus. Other emulsifying devices resemble the
intense types just described, such as special mixing pumps, centrifugal
emulsifiers, ultrasonic generator, slotted mixers, mixing jets including
those in which ultrasonic vibration occurs and turbulent flow devices in
which a coarse emulsion is made to flow along a tube at a speed greater
than the critical velocity for turbulence.
In general, the compositions of the instant invention will comprise from 10
to 90, preferably 30 to 60 wt. % oil phase and the remainder the aqueous
internal phase.
The internal phase may comprise a strong acid or a strong base or any of
the other reagents described in U.S. Pat. No. 3,779,907. However, these
emulsions, as stated above, are especially useful in the process described
in U.S. Ser. No. 382,466. Thus, preferably, in the composition of the
instant invention, the internal phase, is as described therein. Most
preferably the internal phase will comprise either an acid (strong or
regenerable) or a strong base. The concentration of acid or base in the
internal phase of the emulsion is adjusted so that the emulsions may be
used economically. In general, the concentration is as high as possible,
even up to saturation, taking into consideration the stability of the
emulsion, e.g., from 1 to 30% by weight concentrations may be used.
The following are specific embodiments of the instant invention.
EXAMPLE 1
To a vigorously stirred (1,000 to 2,000 RPM) solution of 13.6 of butyl
rubber sulfonated to 2% level in 186.5 g of Solvent Neutral 100 at
85.degree.C. was added dropwise 186 ml of 10% aqueous sulfuric acid
solution. 180 g of the emulsion thus produced was added with stirring (150
to 250 RPM) to 740 ml of water containing 1,720 ppm of NH.sub.4 .sup.+ as
ammonium hydroxide and 2,800 ppm of sulfide as H.sub.2 S. Samples of water
solution were withdrawn by a pipette at 1 minute, 5 minute, 15 minute, 30
minute, 60 minute and 90 minute intervals by allowing the emulsion to
settle and taking a sample of lower aqueous layer. The temperature was
maintained at 80.degree. to 85.degree. throughout the run.
The ammonium concentration gradually reduced to 42 ppm in 30 minutes and
the emulsion was stable over the entire length of experiment (90 minutes).
EXAMPLE 2
The experiment in Example 1 was repeated. The concentrations of NH.sub.4
.sup.+ and S.sup.= were 1,700 ppm and 2,240 ppm, respectively. In this
experiment, steam was passed at 85.degree. through the mixture with
stirring. The concentration of ammonium ions was reduced in 30 minutes to
34 ppm and sulfide ions to <20 ppm. The emulsion was again stable over the
entire length of the experiment (90 minutes).
EXAMPLE 3
The experiment given in Example 1 was repeated using 2.5 wt. % of the
sulfonated butyl rubber in the oil phase. The internal phase contained
2.13 wt. % sulfuric acid. The emulsion was contacted with feed for 5
minutes. The concentration of NH.sub.4 .sup.+ was determined at the
beginning and end of the experiment. After this time, the feed was removed
and the same emulsion was contacted with a fresh feed for 5 minutes. The
process was repeated two more times. The temperature was maintained at
85.degree. for the entire length of the experiment. The concentration of
NH.sub.4 .sup.+ in the four feeds were 118, 137, 143, and 186 ppm and were
reduced to 1, 1, 1.75 and 2 ppm, respectively.
This demonstrates the suitability of single emulsion in repeated
applications.
EXAMPLE 4
The experiment given in Example 1 was repeated with 12% Lubrizol 3702 (a
product of Lubrizol Corp.) in place of sulfonated butyl rubber in the
formulation described therein. The concentration of ammonium ions was
2,040 ppm and that of sulfide ions 1,970 ppm. Within 15 minutes of the
start of the experiment, the entire mass had gelled and samples could not
be withdrawn for ammonium analysis.
EXAMPLE 5
The experiment given in Example 1 was repeated with 4% PIBSA-TEPA, the
reaction product of polyisobutylene-succinic anhydride and
tetraethylene-pentamine (a product of Lubrizol Corp.) and 1% SPAN 80.
Within 15 minutes the entire reaction mixture had gelled and it was not
possible to withdraw samples for ammonium analysis.
EXAMPLE 6
The experiment given in Example 1 was repeated with initial NH.sub.4 .sup.+
concentration of 1,900 ppm but no H.sub.2 S. Within 30 minutes the
concentration of NH.sub.4 .sup.+ was reduced to 3 ppm.
Comparison of Effectiveness of Polymers Sulfonated to Different Levels
EXAMPLE 7
- Unsulfonated Polymer
To a vigorously stirred solution of 13.6 g of butyl rubber (copolymer of
isobutylene with 5 mole % isoprene, same as was used for preparing
sulfonated polymers and 4 g of surfactant Span 80 in 182.4 g of Solvent
Neutral 100 was added dropwise, 166 g of 10% sulfuric acid solution. The
resulting emulsion which looked normal at room temperature was heated to
85.degree. in order to carry out the treatment of sour water. During
heating, the emulsion started breaking and as the temperature reached
80.degree. organic layer separated out completely from aqueous layer. This
demonstrates that the emulsion does not possess any stability under the
operating conditions even though an external surfactant was present.
EXAMPLE 8
- Polymer Sulfonated to 1 Mole % Level
The experiment given in Example 1 was repeated using the same concentration
of butyl rubber sulfonated to 1 mole % level. The initial NH.sub.4 .sup.+
concentration of 1,960 ppm was reduced to 4 ppm within 30 minutes and the
emulsion was stable over the length of the experiment (40 minutes).
EXAMPLE 9
- Polymer Sulfonated to 4 Mole % Level
The experiment given in Example 1 was repeated using the same concentration
of butyl rubber sulfonated to 4 mole % level. The resulting emulsion was
very thick. The initial NH.sub.4 .sup.+ concentration in the feed was
2,040 ppm. Within 15 minutes the entire mass gelled and it was not
possible to carry out the experiment further.
These experiments demonstrate that about 1 mole % sulfonation is desirable
in the sulfonic acid polymers used in preparing the compositions of the
instant invention; however, amounts greater than about 4% are not as
effective.
The experiments given in Examples 9, 10 and 11 were designed to determine
the effect of smaller amount of polymer sulfonated to 4% level on the
stability of the membrane.
EXAMPLE 10
-Polymer Sulfonated to a 4 Mole % Level
An emulsion was prepared by encapsulating 186 g of 10% sulfuric acid
solution in a solution of 1.5 g of butyl rubber sulfonated to 4% level in
198.5 g of Solvent Neutral 100 at 85.degree.C. One half of this emulsion
was contacted with a feed solution containing 1,960 ppm of ammonium
hydroxide in the usual way. The emulsion had a tendency to stick too much
to the sides of the reaction vessel and very poor separability from the
feed water. In effect, quite a significant part of the emulsion could not
be made to contact the feed solution. In order for the emulsion to be
workable, it is important that the emulsion can be easily dispersed in the
form of tiny droplets so as to provide a very large surface area to
effectively and rapidly remove any contaminant. In this case the
concentration of NH.sub.4 .sup.+ was reduced to 80 ppm in 30 minutes but
increased to 100 ppm in 60 minutes, indicating a weakness of the membrane.
EXAMPLE 11
- Polymer Sulfonated to 4 Mole % Level
The experiment given in Example 9 was repeated with 3.0 g of butyl rubber
sulfonated to 4% level instead of 1.5 g as given in the preceding example.
The concentration of NH.sub.4 .sup.+ in the feed was 2,160. This
concentration was reduced to 90 ppm in 30 minutes. However, the emulsion
gelled completely in 55 minutes.
These experiments point out that levels of sulfonated polymer of at least 1
wt. % in the external phase are desirable.
COMPARISON OF EFFECTIVENESS OF SULFONATED POLYMERS WITH DIFFERENT MOLECULAR
WEIGHT
The experiments given in Examples 12-14 were designed to determine the
effect of molecular weight on the membrane strength and their efficacy in
treatment of sour water. It was observed that with concentration of
polymer in the range of 3 to 6% emulsions were very thick pastes and could
not be handled while the emulsions containing very low concentrations of
sulfonated high molecular weight polymer lacked dimensional stability and
had a tendency to gel easily.
EXAMPLE 12
-Isobutylene-Isoprene Copolymer of Molecular Weight 150,000 (Number
Average) Sulfonated to 1 Mole % Level
An emulsion was prepared according to the procedure given in Example 1,
using 0.85% of high molecular weight sulfobutyl (number average 150,000)
instead of 6.8% low molecular weight sulfobutyl (number average 15,000).
It was contacted with a feed solution containing 2,400 ppm of NH.sub.4
.sup.+. The concentration of NH.sub.4 .sup.+ was reduced to 21 ppm in 30
minutes, but soon after this time the entire mass gelled.
EXAMPLE 13
The experiment given in Example 11 was repeated with 0.40% high molecular
weight sulfobutyl. It was contacted with a feed solution containing 2,080
ppm of NH.sub.4 .sup.+. The concentration of NH.sub.4 .sup.+ was reduced
to 145 ppm in 15 minutes. However, the entire mass gelled in 25 to 30
minutes.
EXAMPLE 14
The experiment given in Example 11 was repeated using 1 wt. % sulfoEPT
(number average molecular weight 80,000; prepared by sulfonating
ethylene-propylene-ethylidenenorbornene to 1 mole % level). The
concentration of NH.sub.4 .sup.+ was reduced from 2,040 ppm to 12 ppm in
15 minutes. After 60 minutes, however, the entire mass had emulsified and
the concentration of NH.sub.4 .sup.+ had increased to 25.4 ppm.
These experiments indicate that low molecular weight sulfonic acid polymers
are desirable in preparing compositions of the instant invention, e.g.,
molecular weights of from 5,000 to 50,000.
Salts of Sulfonated Polymers
In order to study the efficacy as additives in liquid membranes, sodium,
ammonium, and potassium salts were prepared by neutralization of low
molecular weight (number average molecular weight 15,000)
isobutylene-isoprene copolymer sulfonated to 1% and 2% level with
corresponding bases. Attempts were made to prepare a 5% solution of these
salts in Solvent Neutral 100. All of these salts were insoluble at
25.degree.C. and 80.degree.C. Of these, the potassium salt of polymer
sulfonated to 2% level displayed the best solubility behavior. Its use in
liquid membrane is described in Example 15.
EXAMPLE 15
A 5% solution of the potassium salt of sulfobutyl (containing 2 mole %
sulfonate groups) was prepared in Solvent Neutral 100 by heating to
85.degree.C. and adding 0.5 cc of Bryj 30 (TM Atlas Chemical Company,
Wilmington, Delaware). An emulsion was prepared from the solution by
encapsulating 83 g of 1% sulfuric acid solution. This emulsion was
contacted with a feed containing 109 ppm NH.sub.4 .sup.+. In 60 minutes
the NH.sub.4 .sup.+ concentration was reduced to 46 ppm. However, the feed
was very cloudy. This demonstrates that these salts may have very marginal
utility as membrane additives in sour water treatment.
Use of Acids Other Than Sulfuric Acid in Sour Water Treatment
EXAMPLE 16
An emulsion was prepared from 100 g of a solution of 6.8 g of sulfobutyl in
Solvent Neutral 100 as oil phase and 83 g of 16.9% polyacrylic acid
(number average molecular weight 50,000 a product of Polysciences, Inc.,
Warrington, Pa.) as the internal phase. The emulsion was contacted with
740 g of an aqueous feed containing 2,400 ppm of NH.sub.4 .sup.+ at
85.degree.. Within 30 minutes the concentration of NH.sub.4 .sup.+ was
reduced to 37.5 ppm and the emulsion was stable over the entire length of
the experiment (90 minutes).
EXAMPLE 17
The experiment given in Example 16 was repeated with 28% aqueous glutaric
acid as internal reagent. The temperature of operation was 85.degree.C.
and the feed contained 2,020 ppm of NH.sub.4 .sup.+ and 1,040 ppm of
H.sub.2 S. After 29 minutes the concentration of NH.sub.4 .sup.+ was
reduced to 78 ppm and H.sub.2 S to less than 20 ppm.
When phosphoric acid or succinic acids are used in the above example
similar results are obtained.
EXAMPLE 18
An emulsion was prepared from 467 g of 175% aqueous polyacrylic acid and
1.75 g of sulfobutyl in 270 g of Solvent Neutral 100. It was contacted
with 1,450 ml of sour water from a refinery containing 2,120 ppm of
NH.sub.4 .sup.+ and 815 ppm S.sup.=. In 19 minutes the concentration of
these ions had dropped to 203 ppm and less than 5 ppm, respectively.
EXAMPLE 19
An emulsion was prepared from 6% by weight of low molecular weight
sulfobutyl 4 wt. % trioctylphosphine oxide, 0.1 wt. % of trioctylamine,
and 90 wt. % of Solvent Neutral 100 as membrane phase and 4.2 wt. % sodium
hydroxide as the aqueous internal phase. The weight ratio of external to
internal phase was 1:1 . 190 g of this emulsion was contacted, with
agitation, with 800 ml of feed, containing 77 ppm of chromium as sodium
dichromate at pH 1.6. Within 5 minutes, the concentration of chromium in
the feed was reduced to less than 0.5 ppm.
The following examples demonstrate the difficulties encountered in trying
to use sulfonated polystyrene, i.e., aromatic sulfonates. It is clear that
these polymers do not dissolve in the solvent systems which are desirably
used and if dissolved in a suitable solvent are precipitated out upon the
addition of the desired solvents.
EXAMPLE 20
To 100 ml of Solvent Neutral 100 was added 2 g of polystyrene sulfonated to
0.81 mole % level. The mixture was magnetically stirred for 24 hours and
then filtered. The residue was washed with isopropanol. It was dissolved
in benzene and precipitated by addition of propanol. The precipitated
solid was collected and dried. The weight of polymer recovered was 2.0 g
which amounts to quantitative recovery.
EXAMPLE 21
The experiment given in Example 20 was repeated using 2 g of polystyrene
containing 2.70 mole % sulfonic acid groups. The recovery of polymer was
almost quantitative.
EXAMPLE 22
The experiment given in Example 21 was repeated with the difference that
the mixture was stirred at 50.degree. to 60.degree.C. The recovery of
polymer was again almost quantitative.
EXAMPLE 23
A solution was prepared by dissolving 1.5 g of polystyrene sulfonated to
0.81 mole % level in 100 ml of xylene. To the solution, 100 ml of Solvent
Neutral 100 was added. The polymer precipitated out as an oil. The
supernatant liquid was decanted off. The polymer was dissolved in 50 ml of
benzene, reprecipitated by pouring into isopropyl alcohol, collected and
dried. The weight of recovered polymer was 1.1 g.
EXAMPLE 24
The experiment given in Example 23 was repeated using 1.5 g of sulfostyrene
containing 2.70 mole % sulfonation. The weight of recovered polymer was
1.35 g.
It must be concluded that polymeric aromatic sulfonic acid derivatives are
unsuitable for preparing the compositions of the instant invention.
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