Note: Descriptions are shown in the official language in which they were submitted.
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Treatment of Hydrocarbons Containing Sulfides
Technical Field
This invention relates to compositions and methods for the removal or other
treatment of hydrogen sulfide and other sulfides present in other
compositions. It
is particularly useful for the removal of sulfides from hydrocarbons,
particularly
oil and gas newly recovered from the earth.
Background of the Invention
Various compositions have been proposed and used for the treatment of
hydrocarbons to remove or otherwise treat hydrogen sulfide and/or other
sulfides
present in them. See, for example, Gatlin's US Patents 5,128,049, 5,486,605,
5,488,103, and 5,498,707, US Patent 4,978,512 in the name of Dillon, and
Stanchem's Canadian Patent 2,269,476.
The treating agents may be referred to as scavengers or sulfide scavengers in
the
patent literature. Frequently they are reaction products of aldehydes and
amine
compounds, and may or may not contain one or more triazines or derivatives
thereof. See the descriptions in columns 5-8 of Trauffler et al US Patent
5,698,171, Sullivan III et al US Patent 5,674,377, 5,674,377 and 5,744,024,
Rivers et al US Patent 5,554,591, Weers et al US Patents 5,223,127, 6,024,866
and 5,284,576, Pounds et al US Patents 5,462,721 and 5,688,478, and Callaway
US Patent 5,958,352. They may be contacted with the hydrocarbons in various
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ways as mentioned in these patents and others such as Galloway US Patent
S,40S,S91 and Fisher US Patent 6,136,282. Our invention may include the use
of any of the sulfide scavengers recited or identif ed in this paragraph and
the
preceding one, as well as any of the sulfide scavengers described in any of
the
S patents discussed herein, particularly those containing at least one
nitrogen.
As reviewed by Trauffer in US Patent 5,698,171, a product of a reaction
between
an aldehyde and a nitrogen compound may be used as a scavenging composition.
Further, he relates that U.S. Pat. No. 2,776,870 discloses that aqueous amines
and
alkanolamines are useful for removing acids from a gaseous mixture. Hydrogen
sulfide may be selectively removed from gas streams containing carbon dioxide
by use of triethanolamine or methyldiethanolamine. British Published Patent
Specification No. 2103645 discloses that hydrogen sulfide and carbon dioxide
may be removed from a gas mixture by contacting the mixture with a solvent
comprising a textiary amine and a physical absorbent. Suitable physical
adsorbents
include N-methylpyrrolidone and sulfolane. U.S. Patent 4,112,0S1 discloses a
process for removing acidic gases from a gaseous mixture with an amine-solvent
liquid absorbent comprising (1) an amine comprised of at least about SO mole
percent of a sterically hindered amine; and (2) a solvent for the amine
mixture
which is also a physical absorbent for the acid gases. Suitable sterically
hindered
amines include various piperidine compounds. Suitable solvents include
sulfones
and pyrrolidone and piperidone compounds, to name a few. U.S. Patent
4,978,512 discloses methods for reducing the levels of hydrogen sulfide and
organic sulfides in a hydrocarbon stream by contacting the stream with a
composition comprising a reaction products of a lower alkanolamine with a
lower
aldehyde. Suitable reaction products include mixtures of triazine and
bisoxazolidine compounds. U.S. Patent 4,647,397 discloses a process and
composition for removing hydrogen sulfide and similar sulfides from a gas
stream. The gas stream is contacted with a substituted aromatic nitrile having
an
electron-attracting substitutent on the aromatic ring at least as strong as
halogen
and an organic tertiary amine in an inert organic solvent, such as N-methyl-2-
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pyrrolidone. The spent contacting solution may be regenerated by heating the
solution above the decomposition temperature of the reaction products to
separate
the sulfides from the liquid phase absorbent solution. U.S. Patent 4,775,519
discloses a continuous process for removing acid gas components from a gas
stream by counter-currently contacting the stream with an aqueous solution of
a
mixture of N-methyldiethanolamine (MDEA) with imidazole or a methyl
substituted imidazole. The gas is de-absorbed from the MDEA and the imidazole
by reducing the pressure and causing the gas to flash. U.S. Patent 4,624,838
discloses a process for removing acid gases from a gaseous stream by
contacting
the stream with an aqueous scrubbing solution containing a hetero nitrogen
compound comprising either a five- or six- membered ring having a pKa no
greater than about 8. Preferred hetero nitrogen compounds include imidazole
and
piperazine compounds. U.S. Patent 5,347,003 describes a regenerative method
where an N-C-N compound is regenerated from a product of a sulfur scavenging
reaction, in which said N-C-N compound removes a sulfur atom from a sulfur
compound to form the original N-C-N compound. U.S. Patent 3,622,273
discloses a regenerative method for the removal of hydrogen sulfide from a
gaseous stream wherein the gaseous stream is contacted with a solution
containing, by weight, from 0.005 to 20 percent of a ferric ion complex, from
25.0
to 99.945 percent of water and from 0.05 to 10.0 percent of a buffering agent
selected from the group consisting of alkali metal carbonate.
Trauffer's review continues: There are numerous patents dealing with the
removal of hydrogen sulfide from liquid or gas streams with various metal
chelates through redox reactions with a higher oxidation state of the metal
followed by oxidative regeneration through the use of air. As a sampling: U.S.
Pat. No. 4,076,621 deals with iron chelates for the removal of hydrogen
sulfide
from water; U.S. Pat. No. 4,414,194 deals with iron chelates with alcohol as a
crystal modifier; U.S. Pat. No. 4,436,714 deals with the use of metal chelates
followed by electrolytic regeneration. All of the patents involving metal
chelates
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describe the use of the metal ion to directly oxidize hydrogen sulfide to a
higher
oxidation state in common.
Trauffer's composition includes a scavenging compound which is a reaction
product of an aldehyde and an nitrogen compound. Typical aldehydes include
formaldehyde, paraformaldehyde, glyoxal, acetaldehyde, butyraldehyde,
benzaldehyde, N-(2-hydroxyethyl)dioxazine and oleylaldehyde, while typical
amines include methylamine, ethylamine, propylamine, isopropyl amine,
oleylamine, ethylene diamine, diethylene tdamine, dimethylamine, diethylamine,
monoethanolamine, diethanolamine, morpholine piperazine,
thiomonoethanolamine and chlorooleylamine.
Trauffer's sulfur scavenging compound is represented by a nitrogen compound of
the formula RIRzNCHR3NR4R5 where each of Rl, R2,R3 R4 and RS is
independently selected from the group consisting of (i) hydrogen; (ii) a
substituted or unsubstituted, saturated or unsaturated, linear, branched or
cyclic
hydrocarbon chain of 1 to 20 carbons; (iii) a substituted or unsubstituted,
saturated '
or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 20
carbons
comprising at least one heteroatom selected from the group consisting of
nitrogen,
oxygen, sulfur and halogen; (iv) a substituted or unsubstituted polymeric
chain;
and (v) a direct bond to any other of Rl, RZ,R3 R4 and R5. Examples of
Trauffer's
suggested scavenging compounds include various triazines, such as 1,3,5-tris(2-
hydroxyethyl)hexahydro-s-triazine, and trimethyl triazine, bisoxazolidines,
such
as N,N'-methylene bisoxazolidine, piperidines, piperazines, amines, such as
methyldiethanolamine, bis(dibutylamino)methane and bis(di-2-
hydroxyethylamino)methane, bis(morpholino)methane, and primary, secondary
and tertiary amines.
Trauffer further describes scavenging compounds as a reaction products between
(a) an aldehyde of formula HCOR where R is selected from the group consisting
of (i) hydrogen; (ii) a substituted or unsubstituted, saturated or
unsaturated,
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linear, branched or cyclic hydrocarbon chain of 1 to 50 carbons; (iii) a
substituted
or unsubstituted, saturated or unsaturated, linear, branched or cyclic
hydrocarbon
chain of 1 to 50 carbons comprising at least one heteroatom selected from the
group consisting of nitrogen, oxygen, sulfur and halogen; (iv) a substituted
or
unsubstituted polymeric chain; (v) a substituted or unsubstituted dimer (vi) a
yono or polyaldehyde. The aldehyde may be utilized in anhydrous or hydrated
forms of the above. Examples of suitable aldehydes include, but are not
limited to:
formaldehyde, paraformaldehyde, . glyoxal, acetaldehyde,butyraldehyde,
benzaldehyde, N-(2-hydroxyethyl)dioxazine, oleylaldehyde and (b) an nitrogen
compound of formula HNR6R~ wherein R6 and R' are independently selected
from the group consisting of: (i) hydrogen; (ii) a substituted of
unsubstituted,
saturated of unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to
50
caxbons; (iii) a substituted or unsubstituted, saturated or unsaturated,
linear,
branched or cyclic hydrocarbon chain of 1 to 50 carbons comprising at least
one
heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and
halogen; (iv) a substituted or unsubstituted polymeric chain; and (v) a direct
bond
to any other of R6 and R~. Examples of suitable nitrogen compounds include,
but
are not limited to methylamine, ethylamine, propylamine, isopropyl amine,
oleylamine, ethylene diamine, diethylene triamine, dimethylamine,
diethylamine,
monoethanolamine, diethanolamine, rnorpholine, piperazine,
thiomonoethanolamine, chlorooleylamine.
The nitrogen compound and the aldehyde of Trauffer's discloure may be reacted
in any molar ratio with a preferred ratio being from 1 mole aldehyde to 10
moles
nitrogen compound to 10 moles aldehyde to 1 mole nitrogen compound, a more
preferred ratio being from 1 mole aldehyde to 5 moles nitrogen compound to 5
moles aldehyde to 1 mole nitrogen compound, an even more preferred ratio being
1 mole aldehyde to 3 moles nitrogen compound to 3 moles aldehyde to 1 mole
nitrogen compound and a most preferred ratio being 1 mole aldehyde to 1 mole
nitrogen compound. The scavenging compound formed from the reaction of the
aldehyde and nitrogen compound are dependent upon the selected nitrogen
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compound, the selected aldehyde and the ratios of each selected. Similarly
mixtures of the above aldehydes and nitrogen compounds may also be reacted in
order to form singular or mixtures of various scavenging compounds. The
reaction of the nitrogen compound and the aldehyde listed above Will typically
result in the formation of an aminal. Aminals typical of those formed in the
described reaction are of the type R1RZNCHR3NRøR5, RiN=CRZR3 and/or
R1R2NCR3R40H where n is an integer from 1 to 1000 and each of Rl, RZ,R3 R4
and RS is independently selected from the group consisting of: (i) hydrogen;
(ii) a
substituted of unsubstituted, saturated of unsaturated, linear, branched or
cyclic
hydrocarbon chain of 1 to 20 carbons; (iii) a substituted or unsubstituted,
saturated
or unsaturated, linear, branched or cyclic hydrocarbon chain of 1 to 20
carbons
comprising at least one heteroatom selected from the group consisting of
nitrogen,
oxygen, sulfur and halogen; (iv) a substituted or unsubstituted polymeric
chain;
and (v) a direct bond to any other of Rl, RZ,R3 R4 and R5. Examples of
scavenging compounds which are useful in scavenging include various triazines,
such as 1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine, and trimethyl
triazine,
bisoxazolidines, such as N,N'-methylene bisoxazolidine, piperidines,
piperazines,
amines, such as methyldiethanolamine, bis(dibutylamino)methane and bis(di-2-
hydroxyethylamino)methane, bis(morpholino)methane, primary, secondary and
tertiary amines, non-generic aminals such as 2,7-dioxa-5,10
diazabicyclo[4.4.0]dodecane, methylaminomethanol, ethylmethyleneimine,
isopropylmethyleneamine.
Gatlin, in US Patent S,I28,049, reviews the prior art partially as follows: In
U.S.
Pat. No. 4,569,766, a method is disclosed for scavenging hydrogen sulfide and
tnercaptans from fluids by contacting the fluids with maleimides. In U.S. Pat.
No. 4,680,127, a method is disclosed for reducing the amount of hydrogen
sulfide
in aqueous or wet gaseous mediums by adding an effective amount of glyoxal,
preferably in combination with formaldehyde or glutaraldehyde. In U.S. Pat.
No.
4,748,011, a method is disclosed for the separation and collection of natural
gas
comprising the use of a sweetening solution. The sweetening solution consists
of
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an aldehyde or a ketone, methanol, an amine inhibitox, sodium or potassium
hydroxides and isopropanol. The amine inhibitor includes alkanolamines to
adjust
the pH. In U.S. Pat. No. 4,978,512, a method is disclosed for selectively
reducing the levels of hydrogen sulfide and organic sulfides present in
gaseous or
liquid hydrocarbon streams or mixtures thereof by contacting the streams with
the
reaction product of a lower alkanolamine and a lower aldehyde.
Gatlin goes on to disclose a two-step scavenging process utilizing scavenging
agents such as hexahydro-1,3,5-tris (2-hydroxyethyl)-S-triazine; tris
(hydroxymethyl) nitromethane; a mixture of 4-(2-nitrobutyl)morpholine and 4,4'
(2-ethyl-2-nitrotrimethylene)-dimorpholine; a mixture of 4,4-
dimethyloxazolidine
and 3,4,4-trimethyloxazolidine; hexahydro-1,3,5-triethyl-S-triazine; a mixture
of
sodium 2-pyridinethiol-1-oxide and hexahydro-1,3,5-tris(2-hydroxyethyl)-S
triazine; 2,2-dibromo-3-nitrilopropionamide; methanol [[[2-(dihydro-5-methyl
3(2H)-oxazolyl)-1-methylethyoxy]methoxy]methoxy];
2[(hydroxymethyl)amino]ethanol; 2[(hydroxymethyl)amino]-2-methyl-propanol;
sodium dichloro-S-triazinetrione dihydrate; or a solution of 1,3-
bis(hydroxymethyl)-5,5-dimethylhydantoin and 1-(hydroxymethyl)-5,5-
dimethylhydantoin. Further, Gatlin reminds us that hexahydro-1,3,5-tris (2-
hydroxyethyl)-S-triazine is commercially available in aqueous solution from
United Industrial Chemicals, Inc. under the tradename UNICIDE TZ-135 and
from Angus Chemical Company under the tradename BIOBAN GK. UNICIDE
TZ-135 is marketed as a fungicide and bactericide for use, by way of example,
in
controlling the growth of bacteria and fungi in oil well drilling and
processing
fluids. BIOBAN GK is also marketed as a bactericide; tris (hydroxymethyl)
nitromethane is commercially available in aqueous solution from Angus Chemical
Company under the tradename .TRIS I~IITRO, and is marketed as an antimicrobial
agent; a mixture of 4-(2-nitrobutyl)morpholine and 4,4'-(2-ethyl-2-
nitrotrimethylene)-dimorpholine is commercially available from Angus Chemical
Company under the tradenames BIOBAN P-1487 or BIOBAN FP, and is
marketed as an antimicrobial agent; a mixture of 4,4-dimethyloxazolidine and
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3,4,4-trimethyloxazolidine is commercially available from Angus Chemical
Company under the tradename BIOBAN CS-1135, and is marketed as
antimicrobial agent for use in oilfield water systems, and as a corrosion
inhibitor.
This material is also available from Cosan Chemical Corporation under the
tradename COSAN 101; hexahydro-1,3,5-triethyl-S-triazine is commercially
available from R. T. Vanderbilt Co., Inc. under the tradename VANICIDE TH,
and is marketed as an industrial preservative; a mixture of sodium 2-
pyridinethiol-
1-oxide and hexahydro-1,3,5-tris(2-hydroxyethyl)-S-triazine is commercially
available from Olin Chemicals under the tradename TRIADINE 10, and is
marketed as an antimicrobial agent; 2,2-dibromo-3-nitrilopropionamide is
commercially available from Dow Chemical U.S.A. under the tradename
DBNPA, and is marketed as a broad spectrum, Iow persistency biocide; methanol
[[[2-(dihydro-5-methyl-3(2H)-oxazolyl)-1-methylethyoxy]methoxy]methoxy] is
commercially a in aqueous solution from Cosan Chemical Corporation under the
tradename Cosan 145, and is marketed as an antimicrobial preservative; 2-
[(hydroxymethyl)amino]ethanol is commercially available from Troy Chemical
Corp. under the tradename TROYSAN 174, and is marlceted as a water-soluble
biocide. This material is also available from Cosan Chemical Corporation under
the tradename COSAN 91; 2[(hydroxymethyl)amino]-2-methyl-propanol is
commercially available from Troy Chemical Company under the tradename
TROYSAN 192, and is marketed as a water-soluble biocide. Sodium dichloro-
S-triazinetrione dihydrate is commercially available from Olin Chemicals under
the tradename OCI 56, and is market for use as a bleach, sanitizer or cleaning
compound. Solutions of 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin,
antibacterial preservatives, may also be used as scavenging agents. Gatlin
prefers
to use dilute solutions of the materials described above as scavenging agents
in
compositions containing from about 1 to about 50 percent, and typically from
about 10 to about 30 percent, of one or more of the preferred active
ingredients
identified above. These dilute solutions of scavenging agents are preferably
added
to the hydrogen sulfide-containing streams at concentrations of about 0.05 to
about 100 ppm of diluted scavenging agent per 1 ppm of hydrogen sulf de, and
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most preferably, at concentrations of from about 2 to about 10 ppm of diluted
scavenging agent per 1 ppm of hydrogen sulfide.
Weers et al, in US Patent 6,024,866, utilize a hydrogen sulfide scavenger
prepared
by reacting an alkylenepolyamine with formaldehyde. They remind us that the
use of various aldehydes which react with hydrogen sulfide has been known in
the
prior art for some time. For example, U.S. Pat. No. 2,426,318 discloses a
method
of inhibiting the corrosive action of natural gas and oil containing soluble
sulfides
on metals by utilizing certain aldehydes, preferably formaldehyde. Depending
on
the size of the alkylene moiety, the scavenger can be water soluble and/or
petroleum hydrocarbon soluble. Having both water solubility and oil solubility
can be advantageous in many case.
The hydrogen sulfide scavengers of the Weers et al disclosure (US Patent
6,024,866) are prepared by reacting alkylenepolyamines and formaldehyde in a
known manner. Where water is present, the alkylenepolyamine is selected so
that
the reaction product is preferably soluble both in water and hydrocarbon
stock.
The polyamines usefial in the preparation of the hydrogen sulfide scavengers
useful in the method of the Weers invention are alkylenepolyamines represented
by the formula HZNRNH(RNH)XH wherein each R is independently an alkylene
radical having 2 to about 20 carbon atoms and x is 0 to about 15. The alkylene
radical may be straight or branched chain, e.g., ethylene, methylethylene,
trimethylene, phenylethylene and may be substituted with one or more organic
or
inorganic radicals that do not react with formaldehyde, e.g., halo such as
chloro,
bromo, fluoro, alkyloxy, etc. As a practical matter, however, the alkylene
radical
is preferably a straight chain lower alkylene, e.g., ethylene or propylene and
any
suitable lower allcyl substituent thereon, such as methyl, ethyl, etc. Where
water
solubility of the scavenger is of lesser importance, the alkylene radical of
the
polyamine may be derived from fatty materials, such as tallow. Representative
polyamines include ethylenediamine, propylenediamine, diethylenetriamine,
triethylenetetramine, tetraethylenepentamine, tetrabutylenepentamine,
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hexaethyleneheptamine, hexapentyleneheptamine, heptaethyleneoctamine,
octaethylenenonamine, nonaethylenedecamine, decaethyleneundecamine,
decahexyleneundecamine, undecaethylenedodecamine,
dodecaethylenetridecamine, tridecaethylenetetradecamine, N-tallow
S propylenediamine and higher polyamines. In general, the scavenging compounds
of the Weers et al 6.024.866 disclosure are prepared by the exothermic
reaction of
an alkylenepolyamine, e.g., diethylenediamine, and formaldehyde. The mole
ratio
of polyamine to formaldehyde may range from about 1:1 to about 1:14,
preferably
about 1:1 to about 1:3. The reaction temperature is maintained at about
SO°-60°C.
10 The reaction may occur over a period of approximately an hour at a time. A
temperature drop indicates the completion of the reaction. The resulting
reaction
product is a complex mixture of compounds, including, for example, methylene-
bridged diethylenetriamines.
1 S In US Patent 5,958,352, Callaway et al propose the use of aldehyde ammonia
trimers as scavengers for sulffiydryl compounds in natural gas. The scavenging
agents of the Callaway invention are aldehyde ammonia trimers that generally
have the following formula:
H
R3 N Rl
HN NH
Ra
2S
.wherein R1, R2, and R3 are independently selected from the group consisting
of
hydrogen and hydrocarbon groups having between about 1-8 carbon atoms,
selected from the group consisting of straight, branched, and cyclic alkyl
groups,
aryl, alkaryl, and aralkyl groups, and heterocyclic alkyls containing oxygen
or
tertiary nitrogen as a ring constituent wherein none of Rl, RZ, or R3 is all
alkoxyalkylene substitutent. In a preferred embodiment, Rl, R2, and R3 are
methyl
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groups. Aldehyde ammonia trimers may be manufactured by reacting
acetaldehyde with aqueous ammonia in a 1:l molar ratio. Water or another
solvent, such as methanol, can be used in the reaction to prevent solid trimer
from
precipitating out of the solution. The amount of water used may vary depending
upon how the product will be used. For example, if the substrate will be
hydrophobic, e.g., a dry oil phase, the trimer may be formulated in
isopropanol
rather than water. In the field, the trimer preferably should be used in a
solution
having an active concentration of about 2-30%, preferably about 10-20%.
I O Galloway, in US Patent 5.405,591, proposes scavenging with a triazine,
which is a
reaction product of an alkanolamine and an aldehyde. The triazine extracts
sulphides) from sour gas to sweeten the gas by reacting with the sulphides) to
form a solution comprised of a sulphonated component and an alkanolamine
component, which substantially separates the sulphonated component from the
alkanolamine component. More aldehyde can be added to the alkanolamine
component to form ~ additional sulphide reactive agent. In this way, a cyclic,
regenerative process is provided. The make-up triazine can be produced from
any
of the following alkanolamines: mono, di, and tri methly amine; mono, di and
tri
ethyl amine; mono di, and tri n-propyl amine; iso proply amine; n, iso, sec,
and
tert butyl amine and ethylenediamine. The make-up triazine can be produced
from any of the following aldehydes: formaldehyde (methanal); acetaldehyde
(ethanal); propinaldehyde (propanal); and n-butyalaldehyde (butanal).
In US Patent 5,554,349, Rivers, et al propose the use of a mixture of amines
made
by reacting an amine compound with an aldehyde compound to reduce the levels
of H2S in liquid or gaseous hydrocarbon streams. At least one of the compounds
must have an alkoxyalkylene radical. The reaction products are trizines having
substituent groups independently selected from hydrogen and an alkyl radical,
including substituted alkyl radicals, of 1 to 5 carbon atoms; where at least
one of
the groups is an alkoxyalkylene group. In another embodiment of the invention,
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the amine mixture may contain other byproducts, such as the monomers which
malce up the hexahydrotriazine, with or without the hexahydrotriazine being
present. These materials are selective to the reduction of H2S levels in
hydrocarbon or aqueous streams in the presence of C02 which does not
compromise their performance.
Amine compounds or reactants proposed by Rivers et al include, but are not
necessarily limited to, 3-methoxypropylamine (CH30CH2CH2CH2NH2;
sometimes noted as MOPA); 3-ethoxypropylamine; ammonia (NH3);
methylamine (CH3NH2); dimethylamine (CH3NHCH3); 1-
methoxyisopropylamine [CH30CH2CH(NH2)CH3, also known by the product
name of Jeffamine Registered TM M-89 amine sold by Texaco Chemical Co.] and
mixtures thereof. The amine reactants to aldehyde reactants molar ratio may
range from about 10:1 to 1:10. It is preferred that the amine to aldehyde
molar
ratio be in the range from about 1.2:1 to 1:1.2. The molar ratio of alkoxy-
alkyleneamine to all other amines used as reactants may range from about 1:0
to
1:100, preferably from about 1:0 to 1:9.
It has been further discovered (as related in Rivers et al US Patent
5,554,349) that
the addition of a dialdehyde at some point in the process has a beneficial
effect.
For example, in one embodiment, the amine compound and the aldehyde
compound are reacted together in a first step and then the dialdehyde is added
in a
second step. At the time of writing, it was unclear whether the dialdehyde is
reacting to give an unknown product or if the dialdehyde was simply blended
with
the reaction products of the amine compound and the aldehyde compound. In any
event, it was observed that the addition of the dialdehyde gives products with
better results for scavenging H2S than when it was absent. Alternatively, the
dialdehyde may be added with the monoaldehyde compound in the first step for
reaction with the amine compound. In yet another embodiment, in the two-step
process, there may be added between the first and second steps the reaction
product of a second amine compound and a second aldehyde compound.
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Generally, the second amine compound is different from the first amine
compound or the secoizd aldehyde compound is different from the second
aldehyde compound, or both. There is no advantage for the second amine
compound and second aldehyde compound to be the same as in the first step.
Suitable dialdehydes for the enhanced embodiment of the invention include, but
are not necessarily limited to, glyoxal; glutaraldehyde; succinic aldehyde;
1,6-
hexane dialdehyde (adipic aidehyde) and mixtures thereof. Glyoxal is
particularly
preferred. Adialdehyde, such as those described above, may be advantageously
blended and/or reacted with known triazine H2S scavengers such as .
Specifically,
the reaction of MEA with CH20 gives 1,3,5-tris-(2-hydroxyethyl)-hexahydro-D-
triazine
In US Patent 5,688,478, Pounds describes a reaction product of an alkanolamine
with a C 1 to C4 dialdehyde, especially ethanedial, for use as a sulfide
scavenger.
Certain prior art is reviewed by Pounds: U.S. Pat. No. 4,978,512 in the name
of
Dillon describes a method for selectively reducing the levels of hydrogen
sulfide
and organic sulfides from gaseous and/or liquid hydrocarbon streams,
particularly
natural gas streams, by contacting the streams with the reaction product of an
alkanolamine with a monoaldehyde. The patent also discloses that the reaction
product may be mixed with a glycol prior to contact with the gas in order to
reduce the water levels in the gas. U.5. Pat. No. 5,128,049 (Gatlin) discloses
a
method of using triazines as hydrogen sulfide scavengers. U.5. Pat. No.
5,169,411 (Weers) discloses a method for preventing liberation of H2S in crude
oil or petroleum residuum medium with imines. U.5. Pat. No. 5,266,185 (Weers)
discloses the suppression of hydrogen sulfides in a heavy hydrocarbon derived
from heavy crude oil by contacting the petroleum with the reaction product of
a
heterocyclic aldehyde and an organic primary amine. The useful compound was
described as an imine. U.5. Pat. No. 5,284,576 (Weers) discloses a process for
scavenging hydrogen sulfide using a scavenger prepared by reacting an
alkylenepolyamine, including diethylenetriamine, and formaldehyde. U.5. Pat.
No. 5,314,672 (Vasil) discloses a method of selectively reducing the levels of
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hydrogen sulfide and organic sulfides by contacting natural gas with the
reaction
product of ethylenediamine and 50% uninhibited aqueous formaldehyde.
Pounds, in the US Patent 5,688,478 discussed above, described a method for
selectively reducing the levels of hydrogen sulfide and organic sulfides
present in
a gas comprising the steps of providing a source of a dialdehyde having two
carbonyl groups; providing a source of an alkanolamine having at least one
hydrogen atom bonded directly to a nitrogen atom; reacting between about 1.5
and about 3 equivalents of hydrogen atoms bonded directly to a nitrogen atom
in
the alkanolamine for every equivalent of carbonyl groups in the dialdehyde to
form a reaction mixture substantially free of triazines; contacting the
sulfides with
a scavenger consisting essentially of the reaction mixture, wherein the
scavenger
is produced at a rate sufficient to reduce the level of sulfides in the gas
contacted
below a given level, and wherein the scavenger flows directly from the
reacting
step to the contacting step; separating the gas from the spent composition;
and
discarding the spent composition. The method requires contacting the
particular
stream with a composition which is a reaction product of an active primary or
secondary amine with an aldehyde. For purposes of the description, an aldehyde
included both monoaldehydes (one carbonyl group) and dialdehydes (two
carbonyl groups). Pounds' preferred monoaldehydes include, but are not limited
to, formaldehyde, acetaldehyde, propionaldehyde (propanal), and n-
butyraldehyde
(1-butanal). The most preferred monoaldehyde is formaldehyde. The preferred
dialdehyde is ethanedial.
In Gatlin's US Patent 5,486,605, a composition is disclosed that is adapted to
convert hydrogen sulfide and organic sulfides to nontoxic polymers. The
compositions comprise amine resin solutions made by reacting sterically
hindered
amines such as amine heads with aldoses selected from the group consisting of
D-
aldoses having from 3 to 6 carbon atoms. Streams containing hydrogen sulfide
or
organic sulfides are preferably treated by contacting such streams with from
about
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2 to about 4 ppm or more of the amine solution of the invention per ppm of
sulfide.
As related by Gatlin, U.S. Pat. Nos. 4,748,011 discloses a method for the
separation and collection of natural gas through use of a sweetening solution
comprising an aldehyde or ketone, methanol, an amine inhibitor (including
alkanolamines), sodium or potassium hydroxides, and isopropanol. Further, U.S.
Pat. Nos. 4,978,512 discloses a method for selectively reducing the levels of
hydrogen sulfide and organic sulfides present in gaseous or liquid hydrocarbon
streams or mixtures thereof by contacting the streams with a composition
comprising the reaction product of a lower alkanolamine with a lower aldehyde.
U.S. Pat. No. 4,112,051 discloses the removal of acidic gases, including
hydrogen
sulfide, from normally gaseous mixtures by contacting the mixtures with an
amine-solvent liquid absorbent comprising an amine having at least about 50
mol
percent of a sterically hindered amine and a solvent for the amine mixtures
which
is also a physical absorbent for the acidic gases.
In Gatlin's US Patent 5,486,605, a hydrogen sulfide or organic sulfide
converter is
provided that comprises the reaction product of sterically hindered amines
such as
selected aliphatic diamines, aliphatic triamines, amino alcohols, and mixtures
thereof with aldoses. According to one preferred embodiment of the Gatlin US
Patent 5,486,605 disclosure, a hydrogen sulfide or organic sulfide converter
is
provided that comprises the reaction product of amine heads with a second
component comprising an aldose selected from the group consisting of D-aldoses
having from three to six carbon atoms. According to another preferred
embodiment of the Gatlin US Patent 5,486,605 disclosure, a hydrogen sulfide or
organic sulfide converter is provided that comprises the reaction product of
amine
heads with a crude aldose mixture made by reacting formaldehyde, methanol,
sodium hydroxide and water. According to another preferred embodiment of the
Gatlin US Patent 5,486,605 disclosure, a hydrogen sulfide or organic sulfide
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converter is made that comprises the reaction product of amine heads with a
second component comprising about 70 parts of 37% formaldehyde containing
about 7 weight percent methanol and about 30 parts of about 50 weight percent
sodium hydroxide in water reacted together slowly while controlling the
temperature between about 1900 % F. and about 210 degrees F., thereafter
cooled,
and adjusted to a pH of between about 6 and 7 by the slow addition of 30%
hydrochloric acid. According to another preferred embodiment of the Gatlin US
Patent 5,486,605 disclosure, a hydrogen sulfide or organic sulfide converter
is
provided that comprises the reaction product of amine heads with an aldose in
a
system further comprising up to about 90 weight percent of a solvent
comprising a
lower alcohol. According to another embodiment of the Gatlin US Patent
5,486,605 disclosure, a composition is provided in which the hydrogen sulfide
or
organic sulfide converter of the invention further comprises a solvent adapted
to
reduce foaming and prevent cross-linking. Preferred solvents include methanol,
methoxymethanol, water, and mixtures thereof. According to another
embodiment of the Gatlin US Patent 5,486,605 disclosure, a composition is
provided in which the hydrogen sulfide or organic sulfide converter of the
invention is diluted with methanol, methoxymethanol, mixtures of methanol and
methoxymethanol, or water, and optionally, a minor amount of a surfactant.
According to another embodiment of the Gatlin US Patent 5,486,605 disclosure,
a
method is provided for removing hydrogen sulfide from gaseous and liquid
hydrocarbon streams by contacting such streams with a solution comprising a
hydrogen sulfide converter (scavenger) of the Gatlin invention as described
above.
.
Use of the compositions and methods described by Gatlin in US Patent 5,486,605
allows direct conversion of hydrogen sulfide to a stable form without
liberating
the hydrogen sulfide during regeneration in the manner experienced with prior
art
compositions and methods. The complexes produced by reacting the compositions
disclosed in Gatlin's US Patent 5,486,605 with hydrogen sulfide do not have to
be
removed from the process fluids for regeneration. The complexes produced
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thereby are largely water soluble, and are therefore easily separated from
gaseous
or liquid hydrocarbon streams.
In US Patent 5,486,605, Gatlin disclosed that compositions which convert
hydrogen sulfide or other organic sulfides to water soluble, nontoxic, stable
complexes can be made by reacting under controlled conditions solutions of
sterically hindered amines comprising amine heads, selected aliphatic
diamines,
aliphatic triamines, amino alcohols, and mixtures thereof, with aldehydes,
aldehyde donors, or the reaction products of lower alkanolamines and lower
aldehydes. The complexes thus formed are easily separated from gaseous or
liquid
hydrocarbons.
Use of the compositions disclosed in Gatlin's US Patent 5,486,605 is said to
be
more efficient than using conventional materials, with significantly lower
concentrations of the converter being required (such as from about 2 to 3
times
less) in actual practice to achieve the same degree of sulfide conversion.
Typical
application ratios for the Gatlin compositions are from about 2 to about 4 ppm
of
converter per ppm of hydrogen sulfide in the treated fluid. This improved
conversion allows more complete removal of hydrogen sulfide at a minimal cost,
often without the need for a scrubber tower, which further reduces related
equipment costs.
Generally speaking, the compositions of Gatlin's US Patent 5,486,605 are
preferably made by reacting a solution comprising free aldehyde and the
reaction
product of a lower aldehyde and a lower alkanolamine either with a solution
comprising a sterically hindered amine, preferably amine heads, or with an
activator comprising the reaction product of a amine heads and formaldehyde. A
particularly preferred lower aldehyde for use in making the subject
compositions
is formaldehyde. A particularly preferred lower alkanolamirie for use in
making
the subject compositions is monoethanolamine. The term "amine heads" refers to
an unrefined mixture of alkyl diamines that comprise from 4 to 6 carbon atoms.
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Examples of alkyl diamines typically found in amine heads include
aminomethylcyclopentylamine; 1,2-cyclohexanediamine (1,2.-
diaminocyclohexane); 1,5-peritanediamine, 2-methyl; 1,6-hexanediamine; 1H-
azepine, hexahydro; and 1,4-butanediamine. Amine heads is commercially
available from Monsanto Company and DuPont as a byproduct in the manufacture
of hexamethylenediamine. Although amine heads is a convenient and useful
source of aliphatic diamines suitable for use in making the scavengers of
Gatlin's
US Patent 5,486,605, it should be understood that other diamines or triamines
not
present in amine heads can likewise be used within the scope of the invention.
Examples of other aliphatic diamines and triamines that can be satisfactorily
used
include 1,4-diaminocyclohexane and bis-hexamethylenetriamine. One
particularly preferred composition is made by reacting amine heads with
formaldehyde. Another preferred composition, as described in Gatlin's US
Patent 5,486,605, is made by reacting amine heads with a solution of free
formaldehyde and the reaction product of monoethanolamine and formaldehyde.
Another preferred composition is made by reacting the reaction product of
monoethanolamine and formaldehyde with an activator comprising the reaction
product of amine heads and formaldehyde. Another composition described by
Gatlin in US Patent 5,486,605 comprises the reaction product of amine heads
with
a formaldehyde donor such as HMTA or hydantoin.
Other materials believed to be satisfactory for use in place of amine heads
include,
for example, methyl-diethanolamine; 2.-[(hydroxymethyl)amino]ethanol, 2-amino-
2-methyl-1-propanol; methylethanol amine; 2-methyl-1-amino ethanol; 2-ethyl-1-
amino ethanol; 2-tertiary butylamino ethanol, 2,-tertiary butylamino ethanol;
2-
amino-2-ethyl-1,3-propanediol; 2-[(hydroxymethyl)amino]-2-methyl propanol;
hydantoin; 5,5-dimethyl-1-hydantoin; acetaldehyde ammonia; acetalsoxime; 2-
amino-2-hydroxymethanol, 1-3-propanediol; 2-amino-1,3-propanediol; 2-amino-
2-methyl-1,3-propanediol; the reaction product of methyl pyrol and
hydroxylamine; choline; and amino-spirocyclic borate esters derived by
reacting
boric acid with glycols, amines and amides.
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Components that may be reacted with sterically hindered amines comprising
amine heads, selected aliphatic diamines, aliphatic triamines, or amino
alcohols to
produce compositions of the Gatlin 5,486,605 patent include, for example,
S aldehydes, aldehyde donors, the reaction products of lower alkanolamines and
lower aldehydes, and the family of D aldoses having from 3 to 6 carbon atoms.
Aldehydes believed to be useful for making the subject compositions are
preferably selected from the group consisting of monoaldehydes and dialdehydes
having from 1 to 6 carbon atoms, and mixtures thereof, with formaldehyde,
acetaldehyde, glycolaldehyde, glyceraldehyde, hydroxymethyl glyceraldehyde,
glyoxal, and methyl formcel (a hemi-acetal, SS percent formaldehyde solution
in
methanol and methoxy-methanol or water) being particularly preferred.
Aldehyde donors suggested by Gatlin in US Patent 5,486,605 as useful in making
1 S scavengers are preferably selected from the group consisting of hydantoin;
hexamethylenetetramine; hexamethylolmelamine; 2-
[(hydroxymethyl)amino]ethanol; S,S-dimethylhydantoin;
tris(hydroxymethyl)nitromethane; 2-vitro-2-methyl-1-propanol; 2-vitro-2-ethyl-
1,3-propanediol; 2-vitro-1-butanol; and acetaldehyde ammonia. D-aldoses having
from 3 to 6 carbon atoms also suggested as useful are preferably selected from
the group consisting of D-Glyceraldehyde; D-Erythrose; D-Ribose; D-Arabinose;
D-Allose; D-Altrose; D-Glucose; D-Mannose; D-Threose; D-Xylose; D-Lyxose;
D-Gulose; D-Idose; D-Galactose; D-Talose; and mixtures thereof.
2S Additional known or proposed sulfide scavengers are (1) the 1,3,5-hexahydro-
1,3,5-tert-butyl triazine of Sullivan III et al US Patent 5,674,377, (2) the
mono-
and polyamidines of Weers et al in US Patent 5,223,127, and (3) the
bisoxazolidines of Rivers in US Patent 6,117,310.
Summary of the Invention
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Our invention includes (a) compositions comprising potassium formate and a
sulfide scavenger and (b) methods of treating sulfide-containing hydrocarbons
by
contacting them with the compositions comprising potassium formate and a
sulfide scavenger. By a sulfide scavenger, we mean any of the compositions
described or suggested for sulfide treatment in any of the patents reviewed in
the
Background of the Invention as well as any other effective sulfide scavenger.
In addition to hydrocarbons such as newly produced crude oil and natural gas,
our
invention may be used to treat other hydrocarbon substrates. The term
"hydrocarbon substrate" is meant to include unrefined and refined hydrocarbon
products, including natural gas, derived from petroleum or from the
liquefaction
of coal, both of which contaiiz hydrogen sulfide or other sulfur-containing
compounds. Thus, particularly for petroleum-based fuels, the term "hydrocarbon
substrate" includes wellhead condensate as well as crude oil which may be
contained in storage facilities at the producing field. "Hydrocarbon
substrate" also
includes the same materials transported from those facilities by barges,
pipelines,
tankers, or trucks to refinery storage tanks, or, alternately, transported
directly
from the producing facilities through pipelines to the refinery storage tanks.
The
term "hydrocarbon substrate" also includes refined products, interim and
final,
produced in a refinery, including distillates such as gasolines, distillate
fuels, oils,
and residual fuels. As used in the claims, the term "hydrocarbon substrate"
also
refers to vapors produced by the foregoing materials.
The scavenging agents of the present invention may be used to treat aqueous
and
hydrocarbon substrates that are rendered "sour" by the presence of "sulfhydryl
compounds," such as hydrogen sulfide (H2S), organosulfur compounds having a
sulfhydryl (-SH) group, known as mercaptans, also known as thiols (R-SH, where
R is a hydrocarbon group), thiol carboxylic acids (RCO-SH), dithio acids (RCS
SH), and related compounds. We include hydrogen sulfide in the term
"sulfhydryl compound."
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As used in this application, the terns "aqueous substrate" refers to any
"sour"
aqueous substrate, including waste water streams in transit to or from
municipal
waste water treatment facilities, tanning facilities, and the like.
Our invention includes a method of treating sulfides in hydrocarbons,
hydrocarbon substrates, or aqueous substrates comprising (a) contacting the
hydrocarbons or substrates containing sulfides with potassium formate and (b)
contacting the hydrocarbons or substrates containing sulfides with a sulfide
scavenger. Contacting of the sulfide-containing hydrocarbon with potassium
formate may take place before the scavenger is used, substantially at the same
time, or after the scavenger is used. The potassium formate is preferably in
an
aqueous solution, but need not be. The scavenger may be any effective sulfide
scavenger, as the primary mechanism of our invention is that the potassium
formate acts to draw water from association with the hydrocarbons, the
sulfides
being themselves associated with the water. The use of potassium formate,
whether or not initially in solution, thus tends to improve the efficiency of
the
scavenging process more or less regardless of the identity of the particular
scavenger.
Typically, sulfides such as hydrogen sulfide in hydrocarbons tend to associate
with whatever water is present with or in contact with the hydrocarbons. Our
invention utilizes the hygrosopic nature of the potassium formate to separate
the
water from the hydrocarbons, which causes the sulfides to come with it, thus
increasing the efficiency of the scavenger when contact is made between the
scavenger and the sulfide. Potassium formate solutions have the additional
advantage of a low freeze point. We are thus able to employ our invention in
climates, remote locations, and temperatures where it is normally difficult to
employ aqueous solutions.
Our invention includes compositions comprising combinations of potassium
formate and sulfide scavengers, with or without additional potassium
hydroxide,
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and the use of these compositions in sulfide removal from hydrocarbons. In
addition, our invention includes the treatment of sewage suspensions, and pulp
systems in the paper industry to reduce sulfide emissions. Our novel
compositions may be used to treat these and other odiferous materials; also,
methods similar to our hydrocarbon-treating methods may be used for sewage,
pulp, and other odiferous compositions and systems, i.e. treating with
potassium
formats and sulfide scavengers in separate steps or at the same time.
'Detailed Description of the Invention
As indicated above, we may use any sulfide scavenger in our process and in our
novel compositions including potassium formats. We prefer to use
amine/aldehyde condensates, and particularly the hydroxy methyl amino alcohols
and other materials described in Gatlin's US Patents 5,486;605 and 5,488,103.
Our invention may be used with any of these and/or any of the scavengers
described in the patents mentioned in the Background of the Invention or in
the
Summary of the invention. Solvents and other materials which may be present
with the scavengers include (without intending to be limiting in any way),
water,
methanol, glycols, and cellosolves.
The aqueous potassium formats solutions and slurnes we use in conjunction with
sulfide scavengers may range in potassium formats concentration from 1 % to
99% by weight, but we prefer solutions from 20% to 40%, and most preferably
25-35%. When used prior to the application of the scavenger, they may be
contacted with the hydrocarbons by continuous injection or in an adsorption
tower. See also the description in Gatlin US Patent 5,128,049 of "pre-
treatment"
and "polishing" steps (column 3, line 62 - column 4, line 36), which are also
useful in the present invention. More than one inj ection or treatment step
may
be used, and different concentrations of the scavenger and the potassium
formats
solution may be used in each.
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Where there is sufficient water in association with the hydrocarbons, very
high
concentrations of potassium formate may be used, and even solid potassium
formate can be useful in circumstances where the solid is likely readily to
contact
the water/sulfide composition. Our invention has the additional advantage that
it
will depress the freeze point of a prepared solution or mixture and can be
readily
used under very cold conditions.
Because of the hygroscopic nature of potassium formate, our process is
particularly useful in treating gaseous hydrocarbons, in that it will tend to
remove
moisture from the gas and/or inhibit the absorption of water by the gaseous
hydrocarbons.
An additional advantage of our process is that the effectiveness of the
scavenger is
prolonged by the alkalinity of the potassium. The potassium formate content of
our treating compositions can be generated in solution by the reaction of
formic
acid and potassium hydroxide, and this solution can be utilized more or less
without additional steps; moreover, the alkalinity of the solution can be
enhanced
by using an excess of potassium hydroxide for the reaction. Potassium
hydroxide
can simply be added to an already prepared solution of potassium formate, also
resulting in enhanced performance of the scavenger.
Whether the potassium formate is combined with the scavenger or used
separately, useful preferred compositions and ratios (separate or premixed) of
the
ingredients include:
1. Scavenger and potassium formate in a weight ratio in the range of
1:9 to 9:1.
2. Preferred ranges for composition 1 include 35-65% scavenger to
65%-35% KCOOH.
3. Compositions 1 and 2 may, and preferably will, include water.
Preferably, the water will be present in amounts to make solutions
of potassium formate in concentrations of 10% to 90% by weight.
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4. Compositions 1, 2, andlor 3 may include KOH, which may be
present as an excess from the reaction of potassium hydroxide with
formic acid to make potassium formate.
The following experiment demonstrates the invention:
Example 1
An adueous solution was prepared by reacting (a) a molar amount of
formaldehyde with (b) a 0.5 molar amount of monoethanolamine and a 0.5 molar
amount of amine heads (the molar calculation being based on the nitrogen
content. An additional 10% by weight of a 60% by weight solution of potassium
formate was introduced, and further diluted with another 15% by weight water.
This solution was placed in a treating vessel including a spreader bar. A gas
containing varying concentrations of hydrogen sulfide evolving from water
separated from a small gas well was bubbled through the solution at a rate of
300-
500 scf/day. The hydrogen sulfide was removed from the gas in amounts as high
as 12,000 ppm based on the gas.
In addition to the uses for the invention mentioned above, our invention bay
be
used to treat drilling fluids, particularly as they are recirculated.
