POLYSULFIDE SOLUTIONS AND HYDROXYALKYL AMINIUM IONS FOR STABILIZING ELEMENTAL SULFUR

SOLUTIONS DE POLYSULFIDES ET IONS HYDROXYALKYLAMINIUMS POUR STABILISER LE SOUFRE ELEMENTAIRE

English Abstract

Hydroxalkylaminium polysulfides are used to provide cold stability to
ammonium polysulfide solutions. Hydroxyalkylaminium sulfides or polysulfides
also
are used to solubilize unwanted sulfur. Preferred aminium ions are
monohydroxyalkylaminium ions, preferably monoethanolaminium ions. When added
to an aqueous stream comprising free cyanide ions (including HCN), the
polysulfide
solution reduces corrosion of metal equipment contacted by the stream by
converting
the free cyanide ions into thiocyanate ions.

Claims

23


We Claim:
1. A composition comprising elemental sulfur complexed with organic
aminium counterions, said composition having the following general formula:
HO-(CH2)n~ N+ R1 R2 R3 S x= R3 R2 R1 N + ~(CH2)n-OH
wherein
n is from about 1 to about 6;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen, hydroxyl groups, up to two aryl groups, alkyl groups having
up to about 6 carbon atoms, and groups having the following general
structure
R4-Y-R5-Z
wherein
R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, R5 and Z are nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, R5 is
selected from the group consisting of hydrogen, a hydroxyl group, an
aryl group, and an alkylene group having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,



24



and an aryl group, Y is nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
-NH group, a sulfur atom, an alkylene group having up to about 6
carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl
group, R5 and Z are nothing;
when R5 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing;
when R5 is alkylene group having up to about 6 carbon atoms, Z is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2 group, and a thiol group; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group.
2. A composition comprising elemental sulfur complexed with organic
aminium counterions, said composition having the following general structure
HO-(CH2)n~ N+ R1 R2 R3 S x= R3 R2 R1 N + ~(CH2)n-OH
wherein
n is from about 2 to about 4;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of


25

hydrogen and substituted and unsubstituted linear and branched alkyl
groups comprising from about 1 to about 6 carbon atoms; and,
wherein two or more of R1, R2, and R3 may be joined to form a group
comprising up to 6 members selected from the group consisting of a
cycloalkyl group and a heterocyclic group.
3. A composition comprising polysulfide ions complexed with
monoethanolaminium ions.
4. An aqueous solution comprising elemental sulfur complexed with
organic aminium counterions having the following general formula:
HO-(CH2)n~ N+ R1 R2 R3 S x= R3 R2 R1 N + ~(CH2)n-OH
wherein
n is from about 1 to about 6;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen, hydroxyl groups, up to two aryl groups, alkyl groups having
up to about 6 carbon atoms, and groups having the following general
structure
R4-Y-R5-Z
wherein
R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;



26



when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, R5 and Z are nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, R5 is
selected from the group consisting of hydrogen, a hydroxyl group, an
aryl group, and an alkylene group having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Y is nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
-NH group, a sulfur atom, an alkylene group having up to about 6
carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl
group, R5 and Z are nothing;
when R5 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing; when R5 is alkylene group having up
to about 6 carbon atoms, Z is selected from the group consisting of a
hydrogen atom, a hydroxyl group, an NH2 group, and a thiol group;
and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group.



27



5. The solution of claim 4 wherein said organic aminium counterions
comprise an amount of said solution sufficient to provide said solution with
cold
stability.
6. The solution of claim 5 wherein said amount is at least about 5 wt.%
of said solution.
7. The solution of claim 5 wherein said amount is at least about 10 wt.%
of said solution.
8. An aqueous solution comprising elemental sulfur complexed with
organic aminium counterions having the following general structure
HO-(CH2)n~ N+ R1 R2 R3 S x= R3 R2 R1 N + ~(CH2)n-OH
wherein
n is from about 2 to about 4;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen and substituted and unsubstituted linear and branched alkyl
groups comprising from about 1 to about 6 carbon atoms; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group.
9. The solution of claim 8 wherein said organic aminium counterions
comprise an amount of said solution sufficient to provide said solution with
cold



28



stability.
10. The solution of claim 9 wherein said amount is at least about 5 wt.%
of said solution.
11. The solution of claim 9 wherein said amount is at least about 10 wt.%
of said solution.
12. An aqueous solution comprising polysulfide ions complexed with
monoethanolaminium ions.
13. The solution of claim 12 wherein said monoethanolaminium ions
comprise an amount of said solution sufficient to provide said solution with
cold
stability.
14. The solution of claim 13 wherein said amount is at least about 5 wt.%
of said solution.
15. The solution of claim 13 wherein said amount is at least about 10 wt.
of said solution.
16. The solution of claim 4 further comprising thiocyanate ions.
17. The solution of claim 8 further comprising thiocyanate ions.
18. The solution of claim 12 further comprising thiocyanate ions.
19. Means for reducing corrosion of metal equipment comprising:
introducing into an aqueous stream comprising cyanide ions an effective
amount of a polysulfide solution under conditions effective to convert
said cyanide ions into thiocyanate ions;



29



wherein said polysulfide solution comprises elemental sulfur complexed with
organic aminium counterions having the following general formula:
HO-(CH2)n~ N+ R1 R2 R3 S x= R3 R2 R1 N + ~(CH2)n-OH
wherein
n is from about 1 to about 6;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen, hydroxyl groups, up to two aryl groups, alkyl groups having
up to about 6 carbon atoms, and groups having the following general
structure
R4-Y-R5-Z
wherein
R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, R5 and Z are nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, R5 is
selected from the group consisting of hydrogen, a hydroxyl group, an
aryl group, and an alkylene group having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Y is nothing;



30



when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
-NH group, a sulfur atom, an alkylene group having up to about 6
carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl
group, R5 and Z are nothing;
when R5 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing;
when R5 is alkylene group having up to about 6 carbon atoms, Z is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2 group, and a thiol group; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group.
20. A method for reducing corrosion of metal equipment comprising:
introducing into an aqueous stream comprising cyanide ions an effective
amount of a polysulfide solution under conditions effective to convert
said cyanide ions into thiocyanate ions;
wherein said polysulfide solution comprises elemental sulfur complexed with
organic aminium counterions having the following general formula:
HO-(CH2)n~ N+ R1 R2 R3 S x= R3 R2 R1 N + ~(CH2)n-OH
wherein


31
n is from about 1 to about 6;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen, hydroxyl groups, up to two aryl groups, alkyl groups having
up to about 6 carbon atoms, and groups having the following general
structure
R4-Y-R5-Z
wherein
R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, R5 and Z are nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, R5 is
selected from the group consisting of hydrogen, a hydroxyl group, an
aryl group, and an alkylene group having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Y is nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group,
an - NH group, a sulfur atom, an alkylene group having up to about 6
carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl


32
group, R5 and Z are nothing;
when R5 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing;
when R5 is alkylene group having up to about 6 carbon atoms, Z is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2 group, and a thiol group; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group.
21. The method of claim 20 wherein said organic aminium counterions
comprise an amount of said polysulfide solution sufficient to provide said
solution
with cold stability.
22. A method for reducing corrosion of metal equipment comprising:
introducing into an aqueous stream comprising cyanide ions an effective
amount of a polysulfide solution under conditions effective to convert
said cyanide ions into thiocyanate ions;
wherein said polysulfide solution comprises elemental sulfur complexed with
organic counterions having the following general formula:
HO-(CH2)n- N+ R1R2R3 Sx- R3 R2 R1N+ -(CH2)n-OH
wherein
n is from about 2 to about 4;



33
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen and substituted and unsubstituted linear and branched alkyl
groups comprising from about 1 to about 6 carbon atoms; and,
wherein two or more of R1, R2, and R3 may be joined to form a group
comprising up to 6 members selected from the group consisting of a
cycloalkyl group and a heterocyclic group.
23. The method of claim 22 wherein said organic counterions comprise an
amount of said polysulfide solution sufficient to provide said solution with
cold
stability.
24. A method for reducing corrosion of metal equipment comprising:
introducing into an aqueous stream comprising cyanide ions an effective
amount of a polysulfide solution under conditions effective to convert
said cyanide ions into thiocyanate ions;
wherein said polysulfide solution comprises elemental sulfur complexed with
monoethanolaminium ions.
25. A method for producing a stabilized polysulfide solution comprising:
mixing a quantity of aqueous hydroxyalkylamine with an amount of hydrogen
sulfide gas effective to produce hydroxyalkylaminium sulfides;
mixing sulfur with said hydroxyalkylaminium sulfides at a ratio of sulfur to
hydroxyalkylaminium sulfides of from about 1:1 to about 9:1 to



34
produce hydroxyalkylaminium polysulfides.
26. The method of claim 25 wherein said hydroxyalkylamine is
monoethanolamine.
27. Means for producing a polysulfide solution comprising polysulfide
ions complexed with organic counterions, wherein said stabilized polysulfide
ions
have the following general formula:
HO-(CH2)n- N+ R1R2R3 Sx- R3R2R1 N+ -(CH2)n-OH
wherein
n is from about 1 to about 6;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen, hydroxyl groups, up to two aryl groups, alkyl groups having
up to about 6 carbon atoms, and groups having the following general
structure
R4-Y-R5-Z
wherein
R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, R5 and Z are nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, R5 is



35
selected from the group consisting of hydrogen, a hydroxyl group, an
aryl group, and an alkylene group having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Y is nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
- NH group, a sulfur atom, an alkylene group having up to about 6
carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl
group, R5 and Z are nothing;
when R5 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing;
when R5 is alkylene group having up to about 6 carbon atoms, Z is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2 group, and a thiol group; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group;
said method comprising:
mixing a quantity of aqueous hydroxyalkylamine with an amount of hydrogen
sulfide gas effective to produce hydroxyalkylaminium sulfides;
mixing sulfur with said hydroxyalkylaminium sulfides at a ratio of sulfur to


36
hydroxyalkylaminium sulfides of from about 1:1 to about 9:1 to
produce hydroxyalkylaminium polysulfides.
28. A method for producing a polysulfide solution comprising polysulfide
ions complexed with organic counterions, wherein said stabilized polysulfide
ions
have the following general formula:
HO-(CH2)n- N+R1R2R3 Sx- R3R2R1N+ -(CH2)n-OH
wherein
n is from about 1 to about 6;
x is from about 2 to about 10; and
R1, R2, and R3 independently are selected from the group consisting of
hydrogen, hydroxyl groups, up to two aryl groups, alkyl groups having
up to about 6 carbon atoms, and groups having the following general
structure
R4-Y-R5-Z
wherein
R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, R5 and Z are nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, R5 is
selected from the group consisting of hydrogen, a hydroxyl group, an


37
aryl group, and an alkylene group having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Y is nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
- NH group, a sulfur atom, an alkylene group having up to about 6
carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl
group, R5 and Z are nothing;
when R5 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing;
when R5 is alkylene group having up to about 6 carbon atoms, Z is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2 group, and a thiol group; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group;
said method comprising:
mixing a quantity of aqueous hydroxyalkylamine with an amount of hydrogen
sulfide gas effective to produce hydroxyalkylaminium sulfides;
mixing sulfur with said hydroxyalkylaminium sulfides at a ratio of sulfur to
hydroxyalkylaminium sulfides of from about 1:1 to about 9:1 to


38
produce hydroxyalkylaminium polysulfides; and,
wherein two or more of R1, R2, and R3 may be joined to form a group comprising
up
to 6 members selected from the group consisting of a cycloalkyl group and a
heterocyclic group.
29. The method of claim 28 wherein said organic counterions comprise an
amount of said polysulfide solution sufficient to provide said polysulfide
solution with
cold stability.

Description

CA 02290249 1999-11-22
194-09282-US
TITLE: POLYSULFIDE SOLUTIONS AND HYDROXYALKYL
AMINIUM IONS FOR STABILIZING ELEMENTAL
SULFUR
Field of the Invention
The present invention relates to organic aminium counterions that are useful
to
prevent polysulfides from precipitating out of aqueous solutions, and to
processes for
using these counterions to produce sulfides, bisulfides, and/or polysulfides
either to
to scavenge elemental sulfur or to prevent polysulfides from precipitating out
of
polysulfide solutions . The invention also relates to polysulfide solutions
comprising
these counterions, and to aqueous streams containing elemental sulfur
complexed with
these counterions. Most preferred streams contain cyanide ions before
treatment, and
comprise thiocyanate ions after treatment.
15 Background of the Invention
Many refinery streams contain hydrogen sulfide and other sulfur-containing
compounds. Many processes are aimed at removing sulfur components. However,
sometimes the presence of sulfur in such refinery streams actually helps to
protect the
iron surfaces of the equipment used to handle this stream. Ammonium bisulfide
20 reacts with iron at the surface of such equipment, forming an iron sulfide
film. Once
formed, the iron sulfide film isolates the iron surface from corrosive
substances, thus
preventing further corrosion.
If cyanide ion is present in the refinery stream, this delicate balance is
disrupted. The cyanide ion reacts with iron ions which are freed from the FeS
at


CA 02290249 1999-11-22
2
194-09282-US
equilibrium to form the very stable hexacyanoferrate (II) complex anion, which
is
water soluble. More and more iron ions are freed from the FeS as the system
strives
for equilibrium. These complexed iron ions are essentially removed as a factor
in
reaching equilibrium, and eventually all of the iron in the FeS film is
released,
exposing the fresh metal surface to corrosion. The problem is particularly
acute in the
sour water from fluid catalytic cracking (FCC) units.
Polysulfides, such as sodium and ammonium polysulfide, are known to control
cyanide ions in waste water streams. Polysulfides convert the cyanide ions
into
noncorrosive, biodegradable thiocyanate ions. Thiocyanate ions do not react
with FeS
and are very water soluble, rendering them readily removable by water washing.
One problem with known polysulfides, such as ammonium polysulfide, is that
they decompose under typical storage conditions, resulting in precipitation of
free
sulfur. As a result, the amount of active ingredient--sulfur--is greatly
reduced, or even
negligible. The precipitated sulfur also can foul or clog valves, pumps and
lines,
leading to expensive corrosion repair problems.
Stabilized polysulfide solutions with good cyanide scavenging capabilities are
needed.
Summary of the Invention
The present invention provides a composition comprising elemental sulfur
2o complexed with organic aminium counterions, said composition having the
following
general formula:
HO-(CHZ)~ N+ R' R2 R3 SX R3 R2 Rl N + - (CH2)"-OH


CA 02290249 1999-11-22
194-09282-US
wherein n is from about 1 to about 6; x is from about 2 to about 10; and R',
R2, and R3
independently are selected from the group consisting of hydrogen, hydroxyl
groups,
up to two aryl groups, alkyl groups having up to about 6 carbon atoms, and
groups
having the following general structure
R4-Y-RS-Z
wherein R4 is selected from the group consisting of hydrogen, a hydroxyl
group, an
aryl group, and alkylene groups having up to about 6 carbon atoms; when R4 is
selected from the group consisting of hydrogen, a hydroxyl group, and an aryl
group,
RS and Z are nothing; when R4 is an alkylene group having up to about 6 carbon
to atoms, RS is selected from the group consisting of hydrogen, a hydroxyl
group, an aryl
group, and an alkylene group having up to about 6 carbon atoms; when R4 is
selected
from the group consisting of hydrogen, a hydroxyl group, and an aryl group, Y
is
nothing; when R4 is an alkylene group having up to about 6 carbon atoms, Y is
selected from the group consisting of a hydrogen atom, a hydroxyl group, an -
NH
15 group, a sulfur atom, an alkylene group having up to about 6 carbon atoms,
provided
that, when Y is a hydrogen atom or a hydroxyl group, RS and Z are nothing;
when RS
is selected from the group consisting of hydrogen, a hydroxyl group, and an
aryl
group, Z is nothing; when RS is alkylene group having up to about 6 carbon
atoms, Z
is selected from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2
20 group, and a thiol group.


CA 02290249 1999-11-22
4
Detailed Descriution of the Invention
194-09282-US
Commercially available forms of polysulfides generally are aqueous
ammonium polysulfide solutions having concentrations of polysulfides in the
range of
from about 30 wt% up to about 70 wt%. These solutions contain polysulfide ions
which--when the solution is added to a cyanide-containing stream--react with
cyanide
ions in the stream to form thiocyanate ions.
The compounds of the present invention are elemental sulfur atoms complexed
with organic aminium ions, which have the following general formula:
HO-(CH2)~ N+ R' R2 R3 SX R3 R2 Rl N + - (CH2)"-OH
wherein
n is from about 1 to about 6, preferably from about 2 to about 4;
x is from about 2 to about 10; and
R', R2, and R3 independently are selected from the group consisting of
hydrogen,
hydroxyl groups, up to two aryl groups, linear, branched, and cyclic alkyl
groups having up to about 6 carbon atoms, and groups having the following
general structure
R4-Y-R5-Z
wherein
2o R4 is selected from the group consisting of hydrogen, a hydroxyl group, an
aryl
group, and alkylene groups having up to about 6 carbon atoms;
when R4 is selected from the group consisting of hydrogen, a hydroxyl group,


CA 02290249 1999-11-22
and an aryl group, RS and Z are nothing;
194-09282-US
when R4 is an alkylene group having up to about 6 carbon atoms, RS is
selected from the group consisting of hydrogen, a hydroxyl group, an
aryl group, and an alkylene group having up to about 6 carbon atoms;
5 when R4 is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Y is nothing;
when R4 is an alkylene group having up to about 6 carbon atoms, Y is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an -
NH group, a sulfur atom, an alkylene group having up to about 6
1 o carbon atoms, provided that, when Y is a hydrogen atom or a hydroxyl
group, R5 and Z are nothing;
when RS is selected from the group consisting of hydrogen, a hydroxyl group,
and an aryl group, Z is nothing;
when RS is alkylene group having up to about 6 carbon atoms, Z is selected
from the group consisting of a hydrogen atom, a hydroxyl group, an
NH2 group, and a thiol group;
wherein two or more of R1, R2, and R3 may join together to form a cyclic or
heterocyclic structure comprising up to 6 members.
In a preferred embodiment, the compound is "hydroxyethylaminium
2o polysulfide," in which n is 2, R', R2, and R3 are hydrogen, and x is from
about 2 to
about 10, most preferably 4.


CA 02290249 1999-11-22
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Although the foregoing gives specific examples of organic aminium ions
encompassed by the present invention, the invention encompasses organic
aminium
ions as long as their amine precursors are water soluble and sufficiently
basic to form
stable alkylaminium sulfide and polysulfide salts. The hydroxyalkylaminium
sulfides
or polysulfides may be used to solubilize unwanted sulfur. The
hydroxyalkylaminium
polysulfides may be used to provide cold stability to ammonium polysulfide
solutions.
Where used to stabilize a polysulfide solution, the solution contains a
sufficient amount of the organic aminium ions to maintain cold stability down
to
l0 temperatures at which the resulting solution will be stored. Such
temperatures will
differ depending upon the customer and the end use for the particular product.
Hydroxyalkylaminium polysulfides are more stable at low temperatures (i.e.,
will
remain soluble in the customer's storage tank even when the temperature drops
to
about 40 °F. or less), and have a much less obnoxious odor than
ammonium
15 polysulfide solutions and the vapors may contain less of the very toxic
H2S.
Polysulfides having the foregoing structure may be made using several
methods. These methods will be described using hydroxyalkylaminium counterions
to form stable polysulfide solutions; however, other organic aminium sulfides
or
polysulfides may be used to solubilize elemental sulfur, whether to form
stable
20 polysulfide solutions or to scavenge unwanted elemental sulfur, using
similar
procedures.


CA 02290249 1999-11-22
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In a preferred method for stabilizing a polysulfide solution using
hydroxyalkylamines, a selected amount of a hydroxyalkylamine is mixed with
hydrogen sulfide gas to produce aqueous hydroxyalkylaminium sulfide and
bisulfide.
The amount of hydroxyalkylamine is selected by the quantity of polysulfide
solution
to be stabilized and the amount of cold stability desired. If a given
application
requires cold stability down to about 0 °F, then the amount of
hydroxyalkylamine
required typically will be about 5 wt.% of the polysulfide solution to be
stabilized. On
the other hand, if the application requires cold stability down to about -20
°F to about -
30°F, then the amount of hydroxyalkylamine required will be from about
10 wt. % to
1 o about 1 S wt. % of the polysulfide solution to be stabilized.
Once the hydroxyalkylamine is mixed with the hydrogen sulfide gas, the
intermediate aqueous solution is mixed with sulfur, preferably with a
stoichiometric
amount of sulfur, such that the mole ratio of sulfur to aminium sulfide
preferably is
about 3:1. Although adducts ranging from 1:1 to 9:1 may conceivably be used
under
15 certain conditions, the primarily 3:1 adduct of hydroxyalkylaminium
polysulfide is
preferred. It may be desirable to then add even more of a hydroxyalkyl amine
or
another water soluble base, such as a hydroxide of an alkali or alkaline earth
metal,
such as sodium or potassium, or any other compatible base , such as
tetramethyl
ammonium hydroxide, in order to raise the pH of the solution to about 10 or
greater,
20 preferably greater than about 10, most preferably about 11.
In another, less efficient method, an ammonium polysulfide solution is mixed


CA 02290249 1999-11-22
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with an amount of hydroxyalkylamine sufficient to achieve cold stability. This
typically requires about 5 wt. % or more, preferably about 10 wt. % or more,
most
preferably about 1 S wt. % or more. The intermediate solution comprises a
combination of (a) monoalkanolamine and ammonium polysulfide and a combination
of (b) hydroxyalkylaminium polysulfide and ammonia.
Where all three of Rl, R2, and R3 are alkyl groups, an aqueous ammonium
polysulfide solution is provided. Again, adducts where the ratio of sulfur to
aminium
sulfide ranges from 1:1 to 9:1 may conceivably be used under certain
conditions, but
the primarily 3:1 adduct of hydroxyalkylaminium polysulfide product is
preferred. An
to amount of hydroxyethyltrialkyl ammonium hydroxide (HO-CH2CH2N+R3 -OH) is
added, preferably an amount which is stoichiometric with the mots of NH4+
present.
Although a stoichiometric amount is preferred, an amount which is more or less
than a
stoichiometric amount also will render the resulting polysulfide solution more
stable
than an ammonium polysulfide solution. If desired, the ammonia may be removed
by
15 sparging from the solution with an inert gas.
The invention is intended to cover the conversion of a stabilizing amount of
polysulfide ions in the subject solutions to hydroxyalkylaminium polysulfide.
In a
preferred embodiment, the amount of polysulfide ions converted to
hydroxyalkylaminium polysulfide is effective to reduce precipitation of free
sulfur
2o and/or aminium or ammonium polysulfide during storage or use at ambient
temperatures for at least about 30 days when compared to ammonium polysulfide


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solutions comprising substantially the same amount of polysulfide which have
not
been stabilized according to the present invention. In a preferred embodiment,
precipitation is reduced at ambient temperatures for at least about 45 days,
most
preferably for at least about 75 days. Crystallization and precipitation of
free sulfur
and the aminium polysulfide from the solution also preferably is reduced at
sub-
ambient temperatures of less than about -9 °C. (15 °F.), most
preferably at less than
about -12 °~C. (10 °F.).
The hydroxyalkylaminium polysulfide may be used in methods of controlling
cyanide ion concentration in any aqueous stream containing such ions. An
example
is the sour process water system of an FCC unit such as taught in U.S. Pat.
No.
4,508,683, incorporated herein by reference. In such water streams or systems,
the
solutions of the present invention are injected into the system at the desired
location,
which readily can be determined by persons of ordinary skill in the art. An
"effective"
amount of the solution is injected. An "effective" amount is an amount which
is
effective to control cyanide ion in the stream, preferably an amount
sufficient to
provide an amount of polysulfide ions which is approximately stoichiometric
with the
amount of cyanide ions.
The pH of the aqueous system being treated preferably is from about 7.5 to
about 9.5, most preferably from about 8.5 to about 9. Acidic pH's are to be
avoided
2o because they promote rapid decomposition of the polysulfides. The amount of
solution added will depend upon the concentration of cyanide ions (including
HCN) in


CA 02290249 1999-11-22
194-09282-US
the aqueous stream being treated, the concentration of the polysulfide in the
solution,
and the degree to which it is desired to reduce the cyanide ions in the
aqueous stream.
The invention will be better understood with reference to the following
5 examples, which are illustrative only and are not intended to limit the
present
invention to a particular embodiment.
EXAMPLE 1
Four samples were prepared containing 100 mmols of (NH4)2S [prepared from
an aqueous solution containing 44.6% (NH4)2S], 300 mmols of sulfur, and at
least 10
10 g of additional water), to result in a solution containing ammonium
polysulfide having
the average formula (NH4)2S4. This ammonium polysulfide solution was soluble
at
room temperature and had an activity of 47%. (The concentration of polysulfide
ions
was 36.7%.)
Two samples were used as controls or "blanks," and two samples were treated
with a stoichiometric amount of monoethanolamine (MEA), i.e., 200 mmols of MEA
per 100 mmol of (NH4)2S. Samples 2 and 4 were sparged for 20 minutes with
nitrogen to remove ammonia and, in sample 2 (containing MEA), to convert the
(NH4)2S4 to (HOCH2CH2NH3)2S4--the hydroxyethylaminium polysulfide. The
solubility of the samples was observed at room temperature and at 5 °C.
The samples
2o were prepared as shown in the following Table:


CA 02290249 1999-11-22
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Calculated
% Polysulfide
(S4'


Calculat-


Sample AdditiveWt of ed Before After


additiveActivity* Sparged Sparging Sparging


(g) (before


sparging)


1 MEA 12.2 61 % No 27% 27%


2 MEA 12.2 61 % Yes 27% 29%*


3 Blank* 17.4 31 % No 24% 24%
* *


(water)


4 Blank* 17.4 31 % Yes 24% Not
* *


(water) applicable


*Calculated activity is the % of all components in water.
**This percentage is based on the assumption that only ammonia is lost during
sparging.
***The additional water was added in order to equal the weight of an amine
component of a different sample not reported in the Table.
The following were the solubility results:
Solubility @
5 C. (41 F.)
at time:


Sample Zero Hours (i.e.,
Room 16.5 hours 1.4 hours
Temperature)


1 Soluble Soluble Soluble


2 Soluble Soluble Soluble


3 Yellow crystals-= --


4 Yellow crystals-- --


to
The foregoing results demonstrate that hydroxyethylaminium polysulfide was


CA 02290249 1999-11-22
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more stable than ammonium polysulfide (by comparing sample 2 with sample 3).
Even at 5 °C. (41 °F.), the hydroxethylaminium polysulfide
solution remained stable.
Without limiting the invention, the enhanced stability was likely due (at
least in part)
to the fact that 2-hydroxyethanamine (MEA) was a stronger base than ammonia at
25
°C:
pKb (HO-CH2CH2-NH2) = 4.5
pKb (NH3) = 4.8
EXAMPLE 2
Cold stability testing was performed on the MEA treated solutions of Example
l0 I by testing the stability of the solutions at the following temperatures:
(41 °F.); (30
°F.); and, (0 °F.). The polysulfides and/or sulfur remained
soluble in both samples
(Sample # l and #2 in Example 1 ), at both temperatures for 68 hours, even
when a
red seed crystal was added to each sample at 22 hours at 0 °F. No
additional
precipitation occurred in either sample even after 9 days, indicating cold
temperature
stability of both samples in the presence or absence of ammonia.
EXAMPLE 3
Four solutions were prepared using stoichiometric amounts of three variable
components: 100% MEA; 42% (NH4)2S; and, 100% sulfur. The following chart gives
the calculation for the stoichiometric amounts used in the experiment:
Ingredient M.W. Grams Millimols


100% MEA 61.1 12.2 200




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Ingredient M.W. Grams Millimols


42% (NH4)2S 68.0 16.2 100


100% Sulfur 32.0 9.6 300


The purpose of this test was to compare the performance of monoethanolaminium
polysulfide to ammonium polysulfide controls where the polysulfide
concentration
was maintained constant in samples A and C and in sparged samples B and D. The
following samples were prepared using varying amounts of MEA:
Composition Composition
before After
sparging Sparging


Sample 100% 42.0% Sulfur D:I. SpargedCalc. Grams Conc.
Hz0 of


MEA (NH4)ZS(g) (g) NH3lostsulfur S4


(g) (g) by presentpresent


sparge* (wt%)


(g)


A 12.2 16.2 9.6 -- No 0 12.8 33.7%


B 12.2 16.2 9.6 -- Yes 3.4 12.8 37.0%


C -- 16.2 9.6 12.2 No 0 12.8 33.7%


D -- 16.2 9.6 12.2 Yes 3.4 12.8 37.0%


*Samples B and D were sparged with nitrogen at a moderate rate for about one-
half hour.
The loss of NH3 could be expected to increase the concentration of polysulfide
ions in
samples B and D to 37.0% (assuming that no hydrogen sulfide was lost from
samples
1o B and D). Some water also would be lost due to sparging, which would also
increase
the concentration of polysulfide ions. Assuming that only ammonia was lost
during


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sparging, one calculated 37% activity for both sparged samples, B and D (last
column,
above).
The foregoing samples were placed in screw cap test tubes and the caps were
tightly sealed with electrical tape so that no vapor could escape during the
test period.
After 24 hours at room temperature, all samples remained soluble. All four
samples
then were placed in a cold bath maintained at 30 °F. and checked at 48
hours. None
of the samples had begun to form a precipitate. Consequently, the samples were
placed in a cold bath maintained at 0 °F. After 24 hours, none of the
samples had
formed a precipitate.
l0 At 24 hours, the samples were "seeded" with either red seed crystals,
assumed
to be monoethanolaminium polysulfide, or yellow seed crystals, assumed to be
ammonium polysulfide, in order to determine if any of the solutions were
supersaturated. "Red seeds" were added to samples A and B. "Yellow seeds" were
added to samples C and D. If the samples were supersaturated, then the
addition of an
appropriate seed crystal should have caused ammonium or monoethanolaminium
polysulfide to crystallize.
No additional precipitate formed at 24 hours after the red seeds were added to
samples treated with MEA (A and B). Subsequent seeding with yellow seeds at 64
hours tested for precipitation of any supersaturated ammonium polysulfide.
After 64
2o hours, the only surviving sample--sample A--was placed in a cold bath
maintained at -
30 °F. for 24 hours. The results are shown in the following Table:


CA 02290249 1999-11-22
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Time Time Time
@ @ @
0
F.


30 -30
F. F.


Sample 48 hrs 24 24 hrs 48 hrs 64 64 hrs 88 hrs 24 hrs
hrs hrs


A no ppt no red no ppt no yellow no ppt no ppt
ppt ppt


seeds seeds


added added


B no ppt no red no ppt no yellow ~/z --
ppt ppt full
of


seeds seeds yellow


added added crystals


C no ppt no yellow ~/z -- -- -- --
ppt full
of


seeds yellow


added crystals


D no ppt no yellow solid -- -- -- --
ppt


seeds mass
of


added yellow


crystals


From the foregoing, the best performing sample was sample A--the MEA
treated/unsparged sample. The sparged MEA-treated sample, or the
monoethanolaminium polysulfide sample (B), arguably was superior to both
sparged
5 and unsparged ammonium polysulfide samples (C and D). However, this
conclusion
is debatable since yellow seeds were added to (C and D) 48 hours before .they
were
added to (B). The observation that yellow crystals (instead of red crystals)
formed in
sample (B) after 88 hours at 0 °F. can only be explained if one assumes
that
monoethanolaminium polysulfide can exist in 2 crystalline forms--one yellow
and one
1 o red--or that sulfiu is precipitating.
EXAMPLE 4
In order to see if sample B was superior to samples C and D of Example 3, all
four samples were allowed to warm to room temperature and then were shaken for
4-


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1/2 hrs with a wrist-action shaker. Samples A and C totally re-dissolved.
Samples B
and D still contained a few undissolved crystals. Then the cooling cycle and
seeding
of Example 3 was repeated, except that both yellow and red crystals were added
concurrently to samples A and C so that supersaturation in either polysulfide
could be
detected at the same time. The results are given in the following Table:
@ Room Time Time
@ 30 @ 0
F. F.


Temp.


Sample 17.5 17.5 41.5 29 hrs 29 hrs 71 hrs
hrs hrs


hrs


A Total no ppt Red & Seed no ppt Red & seeds


solubility yellow crystals yellow dis-


seed dissolved seed solved


crystals crystals


added added


B 1 yellow~10 -- ~10 1,000 -- 10,000


crystal yellow yellow yellow yellow


crystals crystalscrystals crystals


C Total no ppt.Red & Seed no ppt Red & Full
of


solubility yellow crystals yellow red


seed dissolved seed crystals


crystals crystals


added added


D 100 1,000 -- 1,000 10,000 -- Full
of


yellow yellow yellow yellow green


crystalscrystals crystalscrystals yellow


& red


crystals


The foregoing results clearly demonstrate that sample B--the
monoethanolaminium polysulfide--is superior to sample D--the sparged ammonium
polysulfide sample where the initial concentration of polysulfide ions is the
same.


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However, whether B is superior to C cannot be claimed from the above data
since
crystals began to form at a higher temperature in B, but sample C formed much
more
precipitate after 24 hours at 0 °C.
EXAMPLE 5
In order to determine an optimum concentration range for MEA stabilization,
six samples were prepared using varying amounts of MEA. Each sample was split
into two portions, one of which was not sparged and the other of which was
nitrogen
sparged for 1-1/4 hours. The sample preparation parameters are given in the
following Table:
Sample % MEA g 42% g sulfur g MEA mol MEA Calc.
(NH4)ZS per mol MEA aRer
S4 sparging


A 50.0 16.2 9.6 25.8 4.2 53.5


B 40.0 16.2 9.6 17.2 2.8 43.4


C 35.2 16.2 9.6 12.2 2.0 35.3


D 30.0 16.2 9.6 11.1 1.8 33.1


E 25.0 16.2 9.6 8.60 1.4 27.1


F 20.0 16.2 9.6 6.45 1.0 22.4


After preparation and sparging, the samples were placed in screw cap test
tubes. The caps were wrapped with electrical tape to prevent vapor loss. The
samples
first were tested for complete solubility at room temperature. The surviving
samples
were tested at lower and lower temperatures to determine the "winners"--the
samples
with no precipitate at -30 °F. The results are given in the following
Table, in which
unsparged samples are designated with a prime:


CA 02290249 1999-11-22
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194-09282-US
Time Time @ Time
@ room 30 @ 0
temp F.


F.


Sample 0 48 hrs 48 hrs 24 hrs 24 hrs 48 hrs


A no ppt no ppt no ppt no ppt red seedsa few


added crystals


B no ppt no ppt no ppt no ppt red seeds'/z full
. of


added crystals


C a few no change-- -- -- --


crystals


D more no change-- -- -- --


crystals


E many no change-- -- -- --


more


crystals


F very no change-- -- -- --
many


more


crystals



A' no ppt no ppt no ppt no ppt red seedno ppt


added


B' no ppt no ppt no ppt no ppt red seedno ppt


added


C' no ppt no ppt no ppt no ppt red seedno ppt


added


D' no ppt no ppt no ppt no ppt red seedno ppt


added


E' no ppt no ppt no ppt no ppt red seedno ppt


added


F' no ppt no ppt no ppt no ppt red seedno ppt


added


Z o me at room temperature means crystallization occurred in samples C, D, E,
and F during the sparging operation. Note, however, that the samples were
sparged
for 1-1/4 hours instead of the more appropriate'/2 - 3/a hour. As a result,
more water
and possibly H2S was lost than necessary.


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The foregoing results demonstrate that, the more MEA used, the more stable
the solution. However, counterbalancing this enhanced stability with more MEA
is
the fact that less polysulfide is delivered per unit volume of solution. For
commercialization purposes, one would have to balance the cyanide scavenging
ability vs. product stability.
EXAMPLE 6
Tests were performed to determine cold stability using 10 wt. %, 15 wt. % and
20 wt. % MEA in Kerley's "Ammonium Polysulfide KC-20/40" ("APS"), a
commercial aqueous solution of ammonium polysulfide available from Tessenderlo
l0 Kerley. Each sample was prepared by adding 150 g. of the APS to a solution
of MEA
in 8 oz. bottles. The following solutions were tested:
Sam %MEA MEA "KC-20/40 APS"
le


A 0% 0 150


B 10% 16.7 150


C 15% 26.0 150


~D J 20% ~ 37.5g lSOg


As the APS was added, effervescence of NH3 was observed along with a small
rise in temp. (2 - 6 °C.). The bottles were shaken; then about 20 ml.
of each was
poured into a screw cap test tube. To prevent vapor loss, all caps were sealed
with
electrical tape. These 4 tubes were then placed in a Pour Point bath at -28
°C. and
characteristics were observed at the times indicated in the following Table:


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Sample 64 hours
-


seed crystals


15 '/~ 64 hours added to 90 hours 116 hours
hours C &


D


A a few ~2 g of Sacrificed'------ ------


yellow yellow


c stals c stals


B no crystalsno crystalsno crystals150 mg 150 mg


c stals c stals


C no crystalsno crystalsno crystals0 crystal no crystals


growth (seed(seed has


still resentdissolved


D no crystalsno crystalsno crystals0 crystal no crystals


growth (seed(seed has


still resentdissolved


'This sample was taken off test, the supernatant decanted and the red crystals
saved in a bottle under nitrogen. Very small pieces of these crystals were
blotted dry
and used as seeds in samples C & D.
5 From the foregoing, it was concluded that:
1. In the absence of MEA, APS exhibited poor cold stability.
2. All MEA doped samples were much better than the APS.
Since a small amount of crystal growth occurred in the 10 wt. % solution of
MEA, it
is preferred to use MEA at 15 wt. % or 20 wt. %.
~ o EXAMPLE 7
Tests were conducted to compare the cold stability of MEA doped APS vs.
morpholine doped APS. With reference to the Tables below, the samples were
prepared by:
15 1. Adding the appropriate amount of MEA or morpholine to 1 oz. bottles.
2. Following with 15.0 g of Kerley's "KC2040 APS".
3. Shaking 100 times with caps on.


CA 02290249 1999-11-22
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4. Pouring ~ 10 ml of each to a 15 ml screw cap test tube.
194-09282-US
5. Capping tightly and sealing the cap with electrical tape to avoid vapor
loss.
6. Placing in -30 °F. pour point bath.
The samples then were observed periodically, with the following results:
O bservation
@ time....


Sam- 1 Day 1.3
LD. 6 Days
Amine 6 Days


le Da s


A Kerley's AMP ----- no no no Seed
+


0 g amine crystalscrystalscrystalscrystals
(0%)


added


B Kerley's AMP Morpholineno no no Seed
+


1.67 g amine crystalscrystalscrystalscrystals


( 10% added


C Kerley's AMP Morpholineno no no Seed
+


2.65 g amine crystalscrystalscrystalscrystals


1 S% added


D Kerley's AMP Morpholineno no no Seed
+


3.75 g amine crystalscrystalscrystalscrystals


(20% added


E Kerley's AMP MEA no no no Seed
+


1.67 g amine crystalscrystalscrystalscrystals


( 10%) added


1. Notes - Seed crystals came from sacrificed APS control from a previous
experiment (1706-63). The seed crystals were red.
2. The amines used were Aldrich 99+% purity.
to
Observation s added....
@ time
after
seed


Samp 1 Day 2 5 Days
LD. Days
Amine


le


A Kerley's AMP ----- ~ 2 g of ~ 2 g of Full of
+


0 g amine crystals crystals crystals


0%




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194-09282-US
B Kerley's AMP Morpholinelooks likelooks like Definite
+


1.67 g amine crystal crystal growth,crystal


( 10%) growth ~ 10 mg growth,


100 m


C Kerley's AMP Morpholineseeds onlyseeds only seeds
+ only


2.65 g amine


15%


D Kerley's AMP Morpholineseeds onlyseeds only seeds
+ only


3.75 g amine


20%


E Kerley's AMP MEA seeds onlyseeds only seeds
+ only


1.67 g amine


10%


MEA provided superior cold storage stability to morpholine since APS
containing 10% morpholine precipitated whereas APS containing 10% MEA did not.
Persons of ordinary skill in the art will recognize that many modifications
may
be made to the present invention without departing from the spirit and scope
of the
invention. The embodiments described herein are meant to be illustrative only
and
should not be taken as limiting the invention, which is defined in the
following
claims.