U.S. patent application number 10/128066 was filed with the patent office on 2002-10-31 for treatment of hydrocarbons containing sulfides.
This patent application is currently assigned to Clearwater, Inc.. Invention is credited to Gatlin, Larry W., Mueller, Wayne.
Application Number | 20020157989 10/128066 |
Document ID | / |
Family ID | 23099847 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020157989 |
Kind Code |
A1 |
Gatlin, Larry W. ; et
al. |
October 31, 2002 |
Treatment of hydrocarbons Containing Sulfides
Abstract
Potassium formate is used together with a sulfide scavenger to
remove and otherwise treat sulfhydryl compounds such as hydrogen
sulfide present in hydrocarbons and aqueous substrates
Inventors: |
Gatlin, Larry W.;
(Floresville, TX) ; Mueller, Wayne; (Airdrie,
CA) |
Correspondence
Address: |
William L. Krayer
1771 Helen Drive
Pittsburgh
PA
15216
US
|
Assignee: |
Clearwater, Inc.
|
Family ID: |
23099847 |
Appl. No.: |
10/128066 |
Filed: |
April 23, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60286715 |
Apr 25, 2001 |
|
|
|
Current U.S.
Class: |
208/226 ;
208/237; 208/238; 208/240 |
Current CPC
Class: |
C10G 27/06 20130101;
C10G 31/08 20130101; C02F 1/58 20130101; C10G 29/205 20130101; C10G
53/06 20130101; C10G 29/06 20130101; C02F 1/683 20130101; C02F
2303/02 20130101; C10G 29/08 20130101; C10G 33/04 20130101 |
Class at
Publication: |
208/226 ;
208/237; 208/238; 208/240 |
International
Class: |
C10G 029/00; C10G
029/04 |
Claims
1. Method of reducing the level of sulfide impurities present in a
hydrocarbon or hydrocarbon substrate containing a sulfide
comprising contacting the hydrocarbon or hydrocarbon substrate with
potassium formate and a sulfide scavenger.
2. Method of claim 1 wherein said sulfide scavenger comprises a
reaction product of an amine and an aldehyde.
3. Method of reducing the level of sulfide impurities present in a
hydrocarbon also containing water comprising (a) contacting said
hydrocarbon with potassium formate to extract at least some of said
sulfide impurities with at least some of said water from said
hydrocarbon and (b) contacting said water with a sulfide
scavenger.
4. Method of claim 3 wherein said potassium formate is in an
aqueous solution.
5. Method of claim 4 wherein said aqueous solution includes
potassium hydroxide.
6. A composition comprising a sulfide scavenger and potassium
formate in a weight ratio of 1:9 to 9:1.
7. Composition of claim 6 wherein said potassium formate is in an
aqueous solution.
8. A composition of claim 7 including potassium hydroxide.
9. Composition of claim 7 wherein said potassium formate is made by
the reaction in water of potassium hydroxide and formic acid.
10. Composition of claim 8 wherein said potassium hydroxide is in
excess of the molar amount for reaction with said formic acid.
11. Method of scavenging a sulfhydryl compound from a hydrocarbon
substrate containing a sulfhydryl compound or an aqueous substrate
containing a sulfhydryl compound, comprising contacting said
substrate with potassium formate and a sulfide scavenger, said
sulfide scavenger comprising an amine/aldehyde condensate.
12. Method of claim 11 wherein said potassium formate is in aqueous
solution.
13. Method of claim 12 wherein said potassium formate solution
contains potassium hydroxide in addition to said potassium
formate.
14. Method of claim 12 wherein said substrate is a hydrocarbon
substrate and at least two contactings of said substrate are
made.
15. Method of removing a sulfide from an aqueous sulfide-containing
substrate comprising contacting said sulfide-containing composition
with potassium formate and a sulfide scavenger.
16. Method of claim 15 wherein said sulfide-containing composition
is a pulp-containing composition in a paper-making facility.
17. Method of claim 15 wherein said sulfide-containing composition
is a sewage composition.
18. Method of claim 15 wherein said substrate is an aqueous waste
stream from a tanning facility
19. Method of claim 15 wherein said substrate is an aqueous waste
stream from a pulp mill.
20. Method of claim 15 wherein said substrate is a drilling fluid.
Description
RELATED APPLICATION
[0001] This application claims the full benefit of Provisional
Application 60/286,715 filed Apr. 25, 2001, which is incorporated
herein by reference.
TECHNICAL FIELD
[0002] 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
[0003] 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 U.S. Pat. Nos. 5,128,049, 5,486,605, 5,488,103, and
5,498,707, U.S. Pat. No. 4,978,512 in the name of Dillon, and
Stanchem's Canadian Patent 2,269,476.
[0004] 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 U.S. Pat. No.
5,698,171, Sullivan III et al U.S. Pat. Nos. 5,674,377, 5,674,377
and 5,744,024, Rivers et al U.S. Pat. No. 5,554,591, Weers et al
U.S. Pat. Nos. 5,223,127, 6,024,866 and 5,284,576, Pounds et al
U.S. Pat. Nos. 5,462,721 and 5,688,478, and Callaway U.S. Pat. No.
5,958,352. They may be contacted with the hydrocarbons in various
ways as mentioned in these patents and others such as Galloway U.S.
Pat. No. 5,405,591 and Fisher U.S. Pat. No. 6,136,282. All of the
patents identified in this paragraph and the preceding one are
incorporated entirely by reference, as our invention may include
the use of any of the sulfide scavengers recited or identified in
them, particularly those containing at least one nitrogen.
[0005] As reviewed by Trauffer in U.S. Pat. No. 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 tertiary amine and a physical absorbent. Suitable
physical adsorbents include N-methylpyrrolidone and sulfolane. U.S.
Pat. No. 4,112,051 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 50 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. Pat. No. 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.
Pat. No. 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-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. Pat. No.
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. Pat. No. 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. Pat. No. 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. Pat. No. 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.
[0006] 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 describe the use of the metal ion to directly oxidize
hydrogen sulfide to a higher oxidation state in common.
[0007] 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.
[0008] Trauffer's sulfur scavenging compound is represented by a
nitrogen compound of the formula
R.sup.1R.sup.2NCHR.sup.3NR.sup.4R.sup.5 where each of R.sup.1,
R.sup.2, R.sup.3 R.sup.4 and R.sup.5 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 R.sup.1, R.sup.2,
R.sup.3 R.sup.4 and R.sup.5. 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.
[0009] 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, 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 mono 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 HNR.sup.6R.sup.7 wherein R.sup.6 and
R.sup.7 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 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; and (v) a direct bond
to any other of R.sup.6 and R.sup.7. 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, morpholine, piperazine, thiomonoethanolamine,
chlorooleylamine.
[0010] 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 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 R.sup.1R.sup.2NCHR.sup.3NR.sup.4R.sup.- 5,
R.sup.1N.dbd.CR.sup.2R.sup.3 and/or
R.sup.1R.sup.2NCR.sup.3R.sup.4OH where n is an integer from 1 to
1000 and each of R.sup.1, R.sup.2, R.sup.3 R.sup.4 and R.sup.5 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 R.sup.1, R.sup.2, R.sup.3 R.sup.4 and R.sup.5.
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.
[0011] Gatlin, in U.S. Pat. No. 5,128,049, reviews the prior art
partially as follows: In U.S. Pat. No. 4,569,766, a method is
disclosed for scavenging hydrogen sulfide and mercaptans 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 an aldehyde or a ketone, methanol, an amine
inhibitor, 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.
[0012] Gatlin goes on to disclose a two-step scavenging process
utilizing scavenging agents such as hexahydro-1,3,5-tris
(2-hydroxyethyl)-S-triazin- e; tris (hydroxymethyl) nitromethane; a
mixture of 4-(2-nitrobutyl)morphol- ine 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-triazi- ne;
2,2-dibromo-3-nitrilopropionamide; methanol
[[[2-(dihydro-5-methyl-3(2-
H)-oxazolyl)-1-methylethyoxy]methoxy]methoxy];
2[(hydroxymethyl)amino]etha- nol;
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-di- methylhydantoin. 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 NITRO, and is marketed as an antimicrobial agent; a
mixture of 4-(2-nitrobutyl)morpholine and
4,4'-(2-ethyl-2-nitrotrimethylene)-dimorph- oline 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 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-tri-
azine 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-hydr- oxyethyl)-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, low 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 marketed 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-d- imethylhydantoin, 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
sulfide, and most preferably, at concentrations of from about 2 to
about 10 ppm of diluted scavenging agent per 1 ppm of hydrogen
sulfide.
[0013] Weers et al, in U.S. Pat. No. 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.
[0014] The hydrogen sulfide scavengers of the Weers et al
disclosure (U.S. Pat. No. 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 useful in the preparation of the hydrogen sulfide
scavengers useful in the method of the Weers invention are
alkylenepolyamines represented by the formula
H.sub.2NRNH(RNH).sub.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 alkyl 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,
hexaethyleneheptamine, hexapentyleneheptamine,
heptaethyleneoctamine, octaethylenenonamine, nonaethylenedecamine,
decaethyleneundecamine, decahexyleneundecamine,
undecaethylenedodecamine, dodecaethylenetridecamine,
tridecaethylenetetradecamine, N-tallow 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 50.degree.-60.degree. C. 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.
[0015] In U.S. Pat. No. 5,958,352, Callaway et al propose the use
of aldehyde ammonia trimers as scavengers for sulfhydryl compounds
in natural gas. The scavenging agents of the Callaway invention are
aldehyde ammonia trimers that generally have the following formula:
1
[0016] wherein R.sup.1, R.sup.2, and R.sup.3 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 R.sup.1, R.sup.2, or R.sup.3 is an alkoxyalkylene
substitutent. In a preferred embodiment, R.sup.1, R.sup.2, and
R.sup.3 are methyl groups. Aldehyde ammonia trimers may be
manufactured by reacting acetaldehyde with aqueous ammonia in a 1:1
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%.
[0017] Galloway, in U.S. Pat. No. 5.405,591, proposes scavenging
with a triazine, which is a reaction product of an alkanolamine and
an aldehyde. The triazine extracts sulphide(s) from sour gas to
sweeten the gas by reacting with the sulphide(s) 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).
[0018] In U.S. Pat. No. 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, the amine mixture
may contain other byproducts, such as the monomers which make 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 CO2
which does not compromise their performance.
[0019] Amine compounds or reactants proposed by Rivers et al
include, but are not necessarily limited to, 3-methoxypropylamine
(CH3OCH2CH2CH2NH2; sometimes noted as MOPA); 3-ethoxypropylamine;
ammonia (NH3); methylamine (CH3NH2); dimethylamine (CH3NHCH3);
1-methoxyisopropylamine [CH3OCH2CH(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.
[0020] It has been further discovered (as related in Rivers et al
U.S. Pat. No. 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.
[0021] Generally, the second amine compound is different from the
first amine compound or the second 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 CH2O gives 1,3,5-tris-(2-hydroxyethyl)-hexahydro-
-D-triazine
[0022] In U.S. Pat. No. 5,688,478, Pounds describes a reaction
product of an alkanolamine with a C1 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.S. Pat. No. 5,128,049
(Gatlin) discloses a method of using triazines as hydrogen sulfide
scavengers. U.S. Pat. No. 5,169,411 (Weers) discloses a method for
preventing liberation of H2S in crude oil or petroleum residuum
medium with imines. U.S. 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.S. 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.S. Pat. No. 5,314,672 (Vasil) discloses a method of selectively
reducing the levels of hydrogen sulfide and organic sulfides by
contacting natural gas with the reaction product of ethylenediamine
and 50% uninhibited aqueous formaldehyde.
[0023] Pounds, in the U.S. Pat. No. 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.
[0024] In Gatlin's U.S. Pat. No. 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 2 to about 4 ppm or more of
the amine solution of the invention per ppm of sulfide.
[0025] As related by Gatlin, U.S. Pat. No. 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. No.
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.
[0026] 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.
[0027] In Gatlin's U.S. Pat. No. 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
U.S. Pat. No. 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 U.S. Pat. No. 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 U.S. Pat.
No. 5,486,605 disclosure, a hydrogen sulfide or organic sulfide
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 190.degree. 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 U.S. Pat. No. 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 U.S.
Pat. No. 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 U.S. Pat. No. 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 U.S. Pat. No. 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.
[0028] Use of the compositions and methods described by Gatlin in
U.S. Pat. No. 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 U.S. Pat. No. 5,486,605 with
hydrogen sulfide do not have to be removed from the process fluids
for regeneration. The complexes produced thereby are largely water
soluble, and are therefore easily separated from gaseous or liquid
hydrocarbon streams.
[0029] In U.S. Pat. No. 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.
[0030] Use of the compositions disclosed in Gatlin's U.S. Pat. No.
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.
[0031] Generally speaking, the compositions of Gatlin's U.S. Pat.
No. 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 alkanolamine 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.
[0032] Examples of alkyl diamines typically found in amine heads
include aminomethylcyclopentylamine; 1,2-cyclohexanediamine
(1,2-diaminocyclohexane); 1,5-pentanediamine, 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 U.S.
Pat. No. 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 U.S. Pat. No. 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 U.S. Pat. No. 5,486,605 comprises the reaction product of
amine heads with a formaldehyde donor such as HMTA or
hydantoin.
[0033] 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.
[0034] 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, 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, 55
percent formaldehyde solution in methanol and methoxy-methanol or
water) being particularly preferred.
[0035] Aldehyde donors suggested by Gatlin in U.S. Pat. No.
5,486,605 as useful in making scavengers are preferably selected
from the group consisting of hydantoin; hexamethylenetetramine;
hexamethylolmelamine; 2-[(hydroxymethyl)amino]ethanol;
5,5-dimethylhydantoin; tris(hydroxymethyl)nitromethane;
2-nitro-2-methyl-1-propanol; 2-nitro-2-ethyl-1,3-propanediol;
2-nitro-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.
[0036] Additional known or proposed sulfide scavengers are (1) the
1,3,5-hexahydro-1,3,5-tert-butyl triazine of Sullivan III et al
U.S. Pat. No. 5,674,377, (2) the mono- and polyamidines of Weers et
al in U.S. Pat. No. 5,223,127, and (3) the bisoxazolidines of
Rivers in U.S. Pat. No. 6,117,310.
SUMMARY OF THE INVENTION
[0037] 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.
[0038] 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 contain 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.
[0039] 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."
[0040] As used in this application, the term "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.
[0041] 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.
[0042] 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.
[0043] Our invention includes compositions comprising combinations
of potassium formate and sulfide scavengers, with or without
additional potassium hydroxide, 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 formate and
sulfide scavengers in separate steps or at the same time.
DETAILED DESCRIPTION OF TEH INVENTION
[0044] As indicated above, we may use any sulfide scavenger in our
process and in our novel compositions including potassium formate.
We prefer to use amine/aldehyde condensates, and particularly the
hydroxy methyl amino alcohols and other materials described in
Gatlin's U.S. Pat. Nos. 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, all of
which are incorporated by reference. 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.
[0045] The aqueous potassium formate solutions and slurries we use
in conjunction with sulfide scavengers may range in potassium
fornate 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 U.S. Pat. No. 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 injection or treatment step may be used, and different
concentrations of the scavenger and the potassium formate solution
may be used in each.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] Whether the potassium formate is combined with the scavenger
or used separately, useful preferred compositions and ratios
(separate or premixed) of the ingredients include:
[0050] 1. Scavenger and potassium formate in a weight ratio in the
range of 1:9 to 9:1.
[0051] 2. Preferred ranges for composition 1 include 35-65%
scavenger to 65%-35% KCOOH.
[0052] 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.
[0053] 4. Compositions 1, 2, and/or 3 may include KOH, which may be
present as an excess from the reaction of potassium hydroxide with
formic acid to make potassium formate.
[0054] The following experiment demonstrates the invention:
EXAMPLE 1
[0055] An aqueous 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.
[0056] In addition to the uses for the invention mentioned above,
our invention bay be used to treat drilling fluids, particularly as
they are recirculated.
* * * * *