U.S. patent application number 10/498074 was filed with the patent office on 2005-07-21 for nitrogen-containing compounds as corrosion inhibitors.
Invention is credited to Ernest Parr, William John, Overkempe, Kornelis, Speelman, Johanna Christina.
Application Number | 20050156137 10/498074 |
Document ID | / |
Family ID | 20286287 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050156137 |
Kind Code |
A1 |
Overkempe, Kornelis ; et
al. |
July 21, 2005 |
Nitrogen-containing compounds as corrosion inhibitors
Abstract
The present invention relates to nitrogen-containing
hydroxyethyl substituted compounds to be used as corrosion
inhibitors for metal surfaces, for example in aqueous systems and
in particular in oil-field applications, e.g. in oil or gas wells,
and which could be used under sweet-well conditions as well as
under sour-well conditions. It may also be used in oil-field
acidizing and fracture-acidizing well stimulation treatment. The
compounds belong to the group of partly ethoxylated fatty
alkylamines, partly ethoxylated alkyletheramines and partly or
fully hydroxyethyl substituted alkylamdopropylamines. The corrosion
inhibitors have the formula (I) where R is a hydrocarbyl or an acyl
group having 14-24 carbon atoms, or the group
R'OCH.sub.2CH.sub.2CH.sub.2 where R' is a hydrocarbyl group with
14-24 carbon atoms; X is hydrogen, C.sub.2H.sub.4OH or the group Y
is hydrogen or C.sub.2H.sub.4OH and n is 0-3, with the proviso that
at least one of the symbols X and Y is C.sub.2H.sub.4OH, at most
one of the symbols X is n is at least one when R is an acyl group,
and when R is a hydrocarbyl group or the group
R'OCH.sub.2CH.sub.2CH.sub.2 at least one of the symbols X and Y is
hydrogen. 1
Inventors: |
Overkempe, Kornelis;
(Holten, NL) ; Ernest Parr, William John; (Holten,
NL) ; Speelman, Johanna Christina; (Warnsveld,
NL) |
Correspondence
Address: |
Ralph J Mancini
Akzo Nobel Inc.
Intellectual Property Department
7 Livingstone Avenue
Dobbs Ferry
NY
10522-3408
US
|
Family ID: |
20286287 |
Appl. No.: |
10/498074 |
Filed: |
June 9, 2004 |
PCT Filed: |
November 29, 2002 |
PCT NO: |
PCT/EP02/13567 |
Current U.S.
Class: |
252/70 |
Current CPC
Class: |
E21B 41/02 20130101;
C23F 11/142 20130101; C23F 11/145 20130101; C09K 8/54 20130101 |
Class at
Publication: |
252/070 |
International
Class: |
C09K 003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2001 |
SE |
0104176-3 |
Claims
1. A corrosion inhibitor for metal surfaces in an aqueous
environment in oil-field applications which comprises at least one
hydroxyethyl substituted amine having the formula 6where R is a
hydrocarbyl or an acyl group having 14-24 carbon atoms, or the
group R'OCH.sub.2CH.sub.2CH.sub.2 where R' is a hydrocarbyl group
with 14-24 carbon atoms; X is hydrogen, C.sub.2H.sub.4OH or the
group 7Y is hydrogen or C.sub.2H.sub.4OH and n is 0-3, with the
proviso that at least one of the symbols X and Y is
C.sub.2H.sub.4OH, at most one of the symbols X is 8n is at least
one when R is an acyl group, and when R is a hydrocarbyl group or
the group R'OCH.sub.2CH.sub.2CH.sub.2 at least one of the symbols X
and Y is hydrogen.
2. The corrosion inhibitor of claim 1, where R is a hydrocarbyl
group having 16-22 carbon atoms.
3. The corrosion inhibitor of claim 1, where n is 0-2.
4. The corrosion inhibitor of claim 1, where n is 1-2.
5. The corrosion inhibitor of claim 1, where R is the group
R'OCH.sub.2CH.sub.2CH.sub.2, where R' has the same meaning as in
claim 1.
6. The corrosion inhibitor of claim 1, where R is an acyl group
with 14-24 carbon atoms and at least one of the symbols X and Y is
hydrogen.
7. The corrosion inhibitor of claim 1 wherein said amine is of the
formulaR"(C.dbd.O)NHCH.sub.2CH.sub.2CH.sub.2NHCH.sub.2CH.sub.2OH
(VI)where R"(C.dbd.O) is an acyl group with 14-24 carbon atoms.
8. The corrosion inhibitor of claim 1 wherein said aqueous
environment is acidic.
9. The corrosion inhibitor of claim 1 wherein said oilfield
application is under sweet-well conditions.
10. The corrosion inhibitor of claim 1 wherein said oilfield
application is under sour-well conditions.
11. The corrosion inhibitor of claim 1 which comprises a mixture of
ethoxylated amines, wherein the said mixture contains a total of
10-50% of primary amino groups, 10-70% of secondary amino groups
and 10-50% of tertiary amino groups.
12. The corrosion inhibitor of claim 11, wherein the said mixture
contains a total of 10-40% of primary amino groups, 25-65% of
secondary amino groups and 20-40% of tertiary amino groups.
13. The corrosion inhibitor of claim 12, wherein the said mixture
contains a total of 10-35% of primary amino groups, 30-60% of
secondary amino groups and 25-35% of tertiary amino groups.
14. A method for the inhibition of corrosion on ferrous metal
surfaces in an aqueous environment, wherein said method comprises
adding to said environment and/or contacting said ferrous metal
surface with a corrosion inhibiting effective amount of at least
one hydroxyethyl substituted amine having the formula 9where R is a
hydrocarbyl or an acyl group having 14-24 carbon atoms, or the
group R'OCH.sub.2CH.sub.2CH.sub.2 where R' is a hydrocarbyl group
with 14-24 carbon atoms; X is hydrogen, C.sub.2H.sub.4OH or the
group 10Y is hydrogen or C.sub.2H.sub.4OH and n is 0-3, with the
proviso that at least one of the symbols X and Y is
C.sub.2H.sub.4OH, at most one of the symbols X is 11n is at least
one when R is an acyl group, and when R is a hydrocarbyl group or
the group R'OCH.sub.2CH.sub.2CH.sub.2 at least one of the symbols X
and Y is hydrogen.
15. The method of claim 14, where R is a hydrocarbyl group having
16-22 carbon atoms.
16. The method of claim 14, where n is 0-2.
17. The method of claim 16, where n is 1-2.
18. The method of claim 14, where R is the group
R'OCH.sub.2CH.sub.2CH.sub- .2, where R has the same meaning as in
claim 14.
19. The method of claim 14, where R is an acyl group with 14-24
carbon atoms and at least one of the symbols X and Y is
hydrogen.
20. The method of claim 1 wherein said amine is of the
formulaR"(C.dbd.O)NHCH.sub.2CH.sub.2CH.sub.2NHCH.sub.2CH.sub.2OH
(VI)where R"(C.dbd.O) is an acyl group with 14-24 carbon atoms.
Description
[0001] The present invention relates to nitrogen-containing
hydroxyethyl substituted compounds to be used as corrosion
inhibitors for metal surfaces, for example in aqueous systems and
in particular in oil-field applications, e.g. in oil or gas wells,
and which could be used under sweet-well conditions as well as
under sour-well conditions. It may also be used in oil-field
acidizing and fracture-acidizing well stimulation treatment. The
compounds belong to the group of partly ethoxylated fatty
alkylamines, partly ethoxylated alkyletheramines and partly or
fully hydroxyethyl substituted alkylamidopropylamines.
[0002] The use of amines as corrosion inhibitors in different kinds
of systems is well known. Also ethoxylated amines have been
described as components in rust inhibiting compositions, as for
example in U.S. Pat. No. 3,977,994 where a rust inhibiting
composition for metal surfaces is disclosed. This composition
contains a C16-C20 organic acid and a C3-C12 N-alkyl or
N-cycloalkyl-substituted ethanolamine.
[0003] In EP-A1-750 033 a hydraulic fluid composition based on a
boric ester of a glycol ether is disclosed, which comprises a
corrosion-inhibiting system that includes at least one constituent
chosen from fatty mono- di- or polyamines, optionally ethoxylated
in all active positions, or the salts of one or more carboxylic
acids with the said amines, and esters between one or more
carboxylic fatty acids and a polyoxyalkylene glycol.
[0004] EP-A2-903398 describes a method for increasing the corrosion
resistance of a lubricating grease, by the addition of a minor
portion of one or more alkoxylated C1-C30 alkylamines containing
from 0 to 50 moles of alkoxide. All working examples describe
compositions containing alkoxylated fatty amines where all active
positions were substituted with ethylene oxide. Particularly
preferred was the tallow amine derivative with 5 moles of ethylene
oxide.
[0005] BE 841 567 and BE 841 536 disclose N-alkyl-aminoalkanols
where the alkyl chain carries a hydroxy substituent, said compounds
being obtained from (.alpha.-olefin epoxides and amines or
aminoalkanols. These compounds work as corrosion inhibitors in an
aqueous environment.
[0006] In JP 58091176-A N-alkyl substituted alkanolamines with one
or two alkyl chains containing a total of less than 7 carbon atoms
are described as anti-corrosion additives for calcium chloride
brine systems. Among the compounds specifically mentioned are
2-ethylaminoethanol, 2-n-butyl-aminoethanol, 2-dimethylaminoethanol
and 2-diethylaminoethanol. The compounds could also be used in the
presence of a triazole.
[0007] In JP 58021488-A an aqueous hydraulic fluid composition is
disclosed that comprises a sorbitan ester, an alkoxylated
alkylamide, an alkoxylated alkylmonoamine or an alkoxylated
alkylpropylenediamine and water. This hydraulic fluid exhibits a
suitable viscosity and does not rust. The amines disclosed in the
working examples were oleylamine+5EO or N-(tallow
alkyl)propylenediamine+5EO, where all active positions are
substituted by ethylene oxide.
[0008] In U.S. Pat. No. 3,029,125 a process for inhibiting
corrosion in steam and condensate return systems is disclosed,
where alkylene diamines with a hydrocarbyl chain containing 10 to
32 carbon atoms, and that have been hydroxyalkylated with from 1 to
4 moles of a lower alkylene oxide, are used as corrosion
inhibitors. It is stated in column 6 lines 66-71 that optimum
results in evaluating compositions provided in accordance with the
invention have been obtained with fully oxyalkylated long chain
hydrocarbon polyamines in which all of the active hydrogen atoms
attached to nitrogen atoms have been substituted by hydroxy lower
alkyl groups.
[0009] Although a variety of corrosion inhibitors to be used in the
presence of freshwater, seawater or brine has been developed, there
is still a need for more effective corrosion inhibitors and
compositions, especially with the strenuous conditions prevailing
in oil-well applications.
[0010] It has now surprisingly been found that a hydroxyethyl
substituted amine having the formula 2
[0011] where R is a hydrocarbyl or an acyl group having 14-24,
preferably 16-22, carbon atoms, or the group
R'OCH.sub.2CH.sub.2CH.sub.2 where R' is a hydrocarbyl group with
14-24, preferably 16-22, carbon atoms; X is hydrogen,
C.sub.2H.sub.4OH or the group 3
[0012] Y is hydrogen or C.sub.2H.sub.4OH and n is 0-3, preferably
0-2 and most preferably 1-2, with the proviso that at least one of
the symbols X and Y is C.sub.2H.sub.4OH, at most one of the symbols
X is 4
[0013] n is at least one when R is an acyl group, and when R is a
hydrocarbyl group or the group R'OCH.sub.2CH.sub.2CH.sub.2 at least
one of the symbols X and Y is hydrogen;
[0014] can be used as a corrosion inhibitor for metal surfaces,
e.g. in aqueous environments. Various metals, such as iron, copper,
zinc, aluminium and cobalt, as well as alloys, such as brass and
iron-containing alloys, can be protected by said compounds. In
addition they also inhibit scale formation.
[0015] The hydroxyethyl substituted alkylamines or alkyletheramines
of formula (I) are only partly substituted, i.e. not all nitrogen
positions containing active hydrogen atoms are substituted by
hydroxyethyl or polyethylene glycol groups. These compounds are
preferably obtained by ethoxylation of alkylamines or alkyl
etheramines, and will hereafter be referred to as partly
ethoxylated amines. It has surprisingly been found that the said
amines have a much better corrosion-inhibiting ability than the
corresponding unethoxylated or fully ethoxylated amines, where the
phrase "fully ethoxylated amines" refer to amines where all
nitrogen positions containing active hydrogen atoms are substituted
by hydroxyethyl or polyethylene glycol groups.
[0016] Suitable examples of the corrosion inhibitors according to
the present invention are the ethoxylated alkylamines of formula I,
where R is a hydrocarbyl group having 14-24, preferably 16-22,
carbon atoms, and X, Y, and n have the same meaning as above.
[0017] Suitable examples of alkylamines that could be used as
starting materials for the ethoxylated alkylamines are fatty
monoamines according to the formula R1NH.sub.2 (II), where R1 is an
aliphatic group having 14-24, preferably 16-22 carbon atoms; fatty
diamines according to the formula
R2NHCH.sub.2CH.sub.2CH.sub.2NH.sub.2 (III), where R2 is an
aliphatic group having 14-24, preferably 16-22 carbon atoms; linear
fatty triamines according to the formula
R3NHCH.sub.2CH.sub.2CH.sub.2NHCH.sub.2- CH.sub.2CH.sub.2NH.sub.2
(IV), where R3 is an aliphatic group having 14-24, preferably 16-22
carbon atoms; and branched fatty triamines (Y-triamines) according
to the formula R4N(CH.sub.2CH.sub.2CH.sub.2NH.sub- .2).sub.2 (V),
where R4 is an aliphatic group having 14-24, preferably 16-22
carbon atoms. The degree of hydroxyethyl molecular substitution for
the alkylamine corrosion inhibitors of the present invention varies
between 1 up to z-1, where z is the number of active hydrogen atoms
attached to the amino groups. Consequently, when speaking of
specific corrosion inhibiting amino compounds, the indicated number
of ethylene oxide units added to an amino compound is the average
of the number of hydroxyethyl groups introduced into the
molecule.
[0018] Suitable examples of ethoxylated amines according to the
present invention is oleylamine+1EO, (tallow alkyl)amine+1EO, (rape
seed alkyl)amine+1EO, (soya alkyl)amine+1EO, erucylamine+1EO,
N-oleyl-trimethylenediamine+1EO, N-(tallow
alkyl)trimethylenediamine+1EO, N-(rape seed
alkyl)trimethylenediamine+1EO, N-(soya
alkyl)trimethylenediamine+1EO, N-erucyl-trimethylenediamine+1EO,
N-(tallow alkyl)trimethylenediamine+2EO,
N-oleyl-trimethylenediamine+2EO, N-(rape seed
alkyl)trimethylenediamine+2EO, N-(soya
alkyl)trimethylenediamine+2EO, N-erucyl-trimethylenediamine+2EO,
N,N-bis(3-aminopropyl) (rape seed alkyl)amine+1EO,
N,N-bis(3-aminopropyl) (rape seed alkyl)amine+2EO,
N,N-bis(3-aminopropyl) (rape seed alkyl)amine+3EO,
N,N-bis(3-aminopropyl) (tallow alkyl)amine+1EO,
N,N-bis(3-aminopropyl) (tallow alkyl)amine+2EO,
N,N-bis(3-aminopropyl) (tallow alkyl)amine+3EO,
N,N-bis(3-aminopropyl) (soya alkyl)amine+1EO,
N,N-bis(3-aminopropyl) (soya alkyl)amine+2EO,
N,N-bis(3-aminopropyl) (soya alkyl)amine+3EO,
N,N-bis(3-aminopropyl)oleylamine+1EO,
N,N-bis(3-aminopropyl)oleylamine+2EO,
N,N-bis(3-aminopropyl)oleylamine+3E- O,
N-oleyl-N'-(3-aminopropyl)-1,3-propanediamine+1EO,
N-oleyl-N'-(3-aminopropyl)-1,3-propanediamine+2EO,
N-oleyl-N'-(3-aminopropyl)-1,3-propanediamine+3EO, N-(tallow
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+1EO, N-(tallow
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+2EO, N-(tallow
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+3EO, N-(rape seed
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+1EO, N-(rape seed
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+2EO, N-(rape seed
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+3EO, N-(soya
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+1EO, N-(soya
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+2EO, N-(soya
alkyl)-N'-(3-aminopropyl)-1,3-propanediamine+3EO,
N-(3-aminopropyl)-N'-[3-
-(9-octadecenylamino)propyl]-1,3-propanediamine+1EO,
N-(3-aminopropyl)-N'-[3-(9-octadecenylamino)propyl]-1,3-propanediamine+2E-
O,
N-(3-aminopropyl)-N'-[3-(9-octadecenylamino)propyl]-1,3-propanediamine+-
3EO,
N-(3-aminopropyl)-N'-[3-(9-octadecenylamino)propyl]-1,3-propanediamin-
e+4EO, N-(3-aminopropyl)-N'-[3-(rape seed
alkylamino)propyl]-1,3-propanedi- amine+1EO,
N-(3-aminopropyl)-N'-[3-(rape seed alkylamino)propyl]-1,3-propa-
nediamine+2EO, N-(3-aminopropyl)-N'-[3-(rape seed
alkylamino)propyl]-1,3-p- ropanediamine+3EO and
N-(3-aminopropyl)-N'-[3-(rape seed
alkylamino)propyl]-1,3-propanediamine+4EO.
[0019] Other examples of suitable corrosion inhibitors according to
the present invention are the ethoxylated alkyl etheramines of
formula I, where R is the group R'OCH.sub.2CH.sub.2CH.sub.2 where
R' is a hydrocarbyl group with 14-24, preferably 16-22, carbon
atoms, and X, Y, and n have the same meaning as above.
[0020] Suitable examples of alkyl etheramines that could be used as
starting materials for the ethoxylated alkyl etheramines are
R'OCH.sub.2CH.sub.2CH.sub.2NH.sub.2 (VI) and
R'OCH.sub.2CH.sub.2CH.sub.2N- HCH.sub.2CH.sub.2CH.sub.2NH.sub.2
(VII). Especially preferred examples of the ethoxylated alkyl
etheramines are R'OCH.sub.2CH.sub.2CH.sub.2NH.sub.2- +1EO,
R'OCH.sub.2CH.sub.2CH.sub.2NHCH.sub.2CH.sub.2CH.sub.2NH.sub.2+1EO
and
R'OCH.sub.2CH.sub.2CH.sub.2NHCH.sub.2CH.sub.2CH.sub.2NH.sub.2+2EO,
where R' is a hydrocarbyl group with 14-24, preferably 16-22,
carbon atoms, e.g. tallow alkyl, soya alkyl, rape seed alkyl,
octadecenyl or erucyl.
[0021] Further suitable examples of corrosion inhibitors according
to the present invention are the amidoamines of formula I, where R
is an acyl group having 14-24, preferably 16-22, carbon atoms, and
X, Y, and n have the same meaning as above, and at least one of the
symbols X and Y is CH.sub.2CH.sub.2OH. More preferred are the
compounds where at least one of the symbols X and Y is hydrogen.
The most preferred alkyl amidoamines are the monoamido monoamines
5
[0022] where Y is H or C.sub.2H.sub.4OH, provided that at least one
Y is C.sub.2H.sub.4OH, and preferably at least one of the symbols Y
is hydrogen. Examples of compounds VIII are the tallow or rape seed
amide of N,N-bishydroxyethyl-1,3-propylenediamine, obtainable from
the said amine and tallow or rape seed fatty acid respectively.
Especially preferred aminoamides are the monoamido monoamines
R"(C.dbd.O)NHCH.sub.2CH.sub.2CH.- sub.2NHCH.sub.2CH.sub.2OH (IX),
obtainable from N-hydroxyethyl-1,3-propyle- nediamine and a fatty
acid, such as rape seed fatty acid, soya fatty acid, tallow fatty
acid, octadecenoic acid or erucic acid.
[0023] When producing the corrosion inhibitors of the present
invention by ethoxylation of starting materials containing one or
more amino groups, there will invariably be obtained mixtures of
ethoxylated species with a different degree of substitution. These
mixtures of ethoxylated amines, that contain the hydroxyethyl
substituted amines of the invention, will normally contain a total
of 10-50%, preferably 10-40% and most preferably 10-35% of primary
amino groups, 10-70%, preferably 25-65% and most preferably 30-60%
is of secondary amino groups, and 10-50%, preferably 20-40% and
most preferably 25-35% of tertiary amino groups. For example, when
a fatty monoamine according to the formula R1NH.sub.2 (II) is
reacted with 1 mole of ethylene oxide, the result will be a mixture
of ca 33% of unreacted primary amine, 33% of a secondary amine
R1NHCH.sub.2CH.sub.2OH and 33% of a tertiary amine
R1N(CH.sub.2CH.sub.2OH).sub.2. When a fatty diamine according to
the formula R2NHCH.sub.2CH.sub.2CH.sub.2NH.sub.2 (III) is reacted
with 1 mole of ethylene oxide, the mixture obtained will contain
products with a total of 33% primary amino groups, 35% secondary
amino groups and 31% tertiary amino groups. For a product obtained
when a fatty diamine is reacted with 2 moles of ethylene oxide the
distribution will be 12% primary amino groups, 54% secondary amino
groups and 34% tertiary amino groups.
[0024] For corrosion, an especially severe environment is
encountered in gas- and oil-field applications, in particular where
work is done off-shore or on the coast, and where carbon dioxide or
hydrogen sulfide corrosion of ferrous metal surfaces is
particularly troublesome. Even more severe conditions apply when
acid is added in oil-field acidizing and fracture-acidizing well
stimulation treatments. The corrosion inhibitors of the present
invention may be used under sweet-well conditions (brine containing
carbon dioxide) as well as under sour-well conditions (H.sub.2S
present), and with water solutions containing acid. The corrosion
inhibitors will protect the metal surfaces of pipelines, pumps and
other equipment used in the oil wells. The metals to be protected
from corrosion by the corrosion inhibitors are preferably ferrous
metals, such as iron and steel. The corrosion inhibitors may also
work as scale inhibitors.
[0025] The amount of the amine corrosion inhibitor that is required
to obtain a sufficient corrosion protection may vary with the
application where it is used, but is suitably between 2% (w/w) and
2 ppm, preferably between 500 and 2 ppm and most preferably between
120 and 2 ppm.
[0026] In addition to the amine corrosion inhibitors of the present
invention, other ingredients could be added to the corrosion
inhibiting compositions. Examples of such ingredients are organic
or inorganic acids, such as acetic acid, citric acid, hydrochloric
acid and hydrofluoric acid, in which case the amines will be
present as salts; a dispersing surfactant, such as nonionic
ethylene oxide adducts; water-miscible solvents, such as methanol,
ethanol, isopropanol or glycols; scale inhibitors; biocides, such
as quaternary ammonium compounds, e.g. alkyl trimethylammmonium
chlorides; gelling or viscosity-enhancing agents, such as
alkyldimethylamine oxides, alkylamidopropyldimethylamine oxides or
quaternary ammonium salts, e.g. alkylbis(hydroxyethyl)methyl
quaternary ammonium chloride; and other corrosion inhibitors, such
as other amines, amides, or amphoterics.
[0027] The following embodiments illustrate the invention, and they
should not be construed as limiting the scope thereof.
EXAMPLE 1
[0028] The following compounds were assessed for their
substantivity by an ellipsometric technique. In this technique
silicon wafers coated with chromium were placed in an ellipsometric
cell and a solution of the substances in water was added (active
concentration=100 ppm). The adsorption onto chromium was followed
for at least 30 minutes, and the adsorbed mass was calculated.
1TABLE 1 Adsorbed mass Compound (mg/m.sup.2) (Coco alkyl)amine
(Comparison) 1.85 (Tallow alkyl)amine (Comparison) 2.01 (Rape seed
alkyl)amine* (Comparison) 2.04 (Rape seed alkyl)amine* + 1EO 8.50
N-(Coco alkyl)trimethylenediamine (Comparison) 2.07 N-(Coco
alkyl)trimethylenediamine + 1EO 4.5 (Comparison) N-(Coco
alkyl)trimethylenediamine + 2EO 3.7 (Comparison) N-(Coco
alkyl)trimethylenediamine + 3EO 2.7 (Comparison) N-(Tallow
alkyl)trimethylenediamine 1.89 (Comparison) N-(Tallow
alkyl)trimethylenediamine + 1EO 5.2 N-(Tallow
alkyl)trimethylenediamine + 2EO 4.3 N-(Tallow
alkyl)trimethylenediamine + 3EO 1.3 (Comparison) N-(Rape seed
alkyl)*trimethylenediamine 2.41 (Comparison) N-(Rape seed
alkyl)*trimethylenediamine + 1EO 4.6 N-(Rape seed
alkyl)*trimethylenediamine + 2EO 4.5 N,N-bis(3-aminopropyl)(tallow
alkyl)amine 0.92 (Comparison) N,N-bis(3-aminopropyl)(tallow
alkyl)amine + 1EO 5.04 N,N-bis(3-aminopropyl)(tallow alkyl)amine +
2EO 4.64 N,N-bis(3-aminopropyl)(tallow alkyl)amine + 3EO 4.53 *from
low erucic rape seed oil
[0029] From Table 1 it is evident that the adsorbed mass is greater
when the amine has greater secondary characteristics. If the amine
is fully substituted with ethylene oxide, to give an amine with
tertiary characteristics, or if the amine is not substituted with
ethylene oxide at all, the level of adsorption falls below that of
a partially substituted amine. A low adsorption would mean that the
compound is unlikely to be effective as a corrosion inhibitor.
EXAMPLE 2
[0030] A series of corrosion measurements were performed by the
"bubble test method". In these a simulated "Forties" brine was used
(Forties is an oil-field in the North Sea), which was saturated
with CO.sub.2 (pH ca 5.3), the test electrodes were typical
pipeline steel (Grade API 5L X52 polished to 600 grit finish), the
temperature was 50.degree. C., and the solution was continuously
stirred.
[0031] Forties Brine Composition:
[0032] Quantity of salts for 1 litre of simulated Forties brine
2 Na.sub.2SO.sub.4 0.016 g NaCl 74.14 g NaHCO.sub.3 0.68 g
MgCl.sub.2*6H.sub.2O 4.21 g CaCl.sub.2*6H.sub.2O 17.19 g KCl 0.71
g
[0033] Procedure:
[0034] The brine solution was introduced into the test vessel, and
the vessel was de-aerated by purging with CO.sub.2 overnight. The
temperature was then set at 50.degree. C., and the pressure of
CO.sub.2 was kept at 1 bar. The polished electrode was degreased,
rinsed and dried, after which it was put into the electrode holder
and inserted into the test cell. The magnetic stirrer was started
and a baseline corrosion rate was established by measuring the
Linear Polarisation Resistance every 30 minutes (4-5 hours). Then
the compounds to be investigated were introduced by injection into
the solution at the concentrations specified in Table 2 using a
micropipette. The corrosion rate was followed until it stabilised.
The % protection was then calculated from the following
equation:
% protection=(1-(x/y))*100
[0035] where
[0036] x=corrosion rate in the presence of corrosion inhibitor
(mm/year)
[0037] y=corrosion rate in the absence of corrosion inhibitor
(mm/year)
3 TABLE 2 % protection Compound 10 ppm 50 ppm 100 ppm (Tallow
alkyl)amine + 1EO 89.7 86 (Rape seed alkyl) *amine + 1EO 91.4 92
94.5 N-(Coco alkyl)trimethylenediamine + 1EO -20.3 (Comparison)
N-(Coco alkyl)trimethylenediamine + 2EO -28.7 (Comparison)
N-(Tallow alkyl)trimethylenediamine + 85 89.5 93.5 1EO N-(Tallow
alkyl)trimethylenediamine + 77.1 87 89.5 2EO N-(Rape seed alkyl) *-
94.7 96 trimethylenediamine + 1EO N-(Rape seed alkyl) *- 93 98.7
trimethylenediamine + 2EO N,N-bis(3-aminopropyl)(rape 81.1 seed
alkyl)*amine + 2EO N-(Rape seed alkyl) **- 90.7 trimethylenediamine
+ 1EO N-(Rape seed alkyl) **- 82.3 trimethylenediamine + 2EO *from
low erucic rape seed oil **from high erucic rape seed oil
[0038] The table shows that particularly good protection is
obtained with compounds having long alkyl groups with a high degree
of unsaturation. For example the N-(Rape seed
alkyl)trimethylenediamine+1 or 2EO (derived from low erucic rape
seed oil) afford an excellent corrosion protection, which is very
surprising since the comparative examples with products containing
a coco alkyl chain do not afford any protection at all.
EXAMPLE 3
[0039] Corrosion measurements for some hydroxyethyl substituted
aminoamides were performed by the same procedure as described in
Example 2.
4 TABLE 3 % protection Compound 10 ppm 50 ppm 100 ppm
Tallow-CONH(CH.sub.2).sub.3NHCH.sub.2CH.sub.2O- H 78.0 96.0 97.5
Tallow-CONH(CH.sub.2).sub.3N(CH.sub.2CH.sub.2OH).s- ub.2 59.5 93.5
93.5
[0040] Both of the aminoamide compounds in the table above are very
efficient as corrosion inhibitors at 50 ppm and higher. During the
test conditions the aminoamide compound where the amino group
nitrogen is secondary is somewhat more efficient, especially at low
concentrations, than the aminoamide compound where the amino group
nitrogen is tertiary.
EXAMPLE 4
[0041] Corrosion rate measurements were performed under more severe
conditions, where the electrodes were suspended in a rotating cage
in an autoclave. The brine solution composition was the same as in
example 2. The electrode was prepared from API 5L X52 grade steel
and polished to 600 grit. The temperature was kept at 80.degree.
C., and the vessel was pressurized with 2 bar of CO.sub.2.
[0042] Procedure:
[0043] The electrode was placed in the cell, and the cell was
flushed with CO.sub.2. The brine solution, that had been
de-aerated, was transferred into the cell under a CO.sub.2 blanket.
The rotation speed was set to achieve the required wall shear
stress. The temperature was set at 80.degree. C., and the cell was
continuously purged with CO.sub.2. A baseline corrosion rate was
established by measuring the Linear Polarisation Resistance. When a
stable baseline had been established, the compounds to be
investigated were introduced by injection into the solution at the
concentrations specified in Table 4 using a micropipette. The
corrosion rate was followed until it stabilised. The % protection
was calculated by the equation used in examples 2 and 3.
[0044] As a comparison N-(Tallow alkyl)-trimethylenediamine+3EO,
which is mentioned as one preferred compound in U.S. Pat. No.
3,029,125, was used.
5 TABLE 4 % protection Compound 50 ppm 100 ppm 150 ppm (Rape seed
alkyl) *amine + 1EO 95.0 95.0 95.0 N-(Rape seed alkyl) *- 90.5 95.0
91.0 trimethylenediamine + 1EO N-(Rape seed alkyl) *- 95.0 95.0
95.5 trimethylenediamine + 2EO N-(Tallow alkyl)-trimethylenediamine
+ 65.9 70.7** 3EO (comparison) Tallow-CONH(CH.sub.2).sub.3-
NHCH.sub.2CH.sub.2OH 94.5 98.0 98.0 (Rape seed) 95.1 97.8 98.4
*--CONH(CH.sub.2).sub.3NHCH.sub.2CH.sub.2OH (Rape seed) 92.7 93.7
95.0 *--CONH(CH.sub.2).sub.3N(CH.sub.2CH.sub.2OH).sub.2 *from low
erucic rape seed oil **measured at 200 ppm
[0045] The hydroxyethyl substituted amines according to the
invention exhibited excellent corrosion protection also under the
severe conditions prevailing in this test. The comparison test
showed that the corrosion protection obtained by the prior art
compound was inferior to the protection obtained from the compounds
according to the invention.
* * * * *