Note: Descriptions are shown in the official language in which they were submitted.
~0l~6~
The presen-t invention relates to a new inhibitor
composition useful for preventing corrosion by solvents
used in treating sour gas streams and to the inhibited
solvent.
The conditioning of naturally occurring and
; 5 synthetic gases by absorbing acidic gases such as CO2,
H2S, COS, and HCN in an absorbent solution has been
practiced commercially for many years. Gases such as
`~ feed gas for an ammonia plant, natural gas, and fluegas are examples. Aqueous solutions of various compounds
such as alkanolamines, sulfolane (tetrahydrothiophene-
l,l-dioxide), potassium carbonate, and mixtures of
two or more of these have been used for the purpose.
The water may be replaced partly or entirely by a ~-
glycol. All of these systems are plagued by corrosion
15 ~ of metal equipment which can be caused by products
~; of degradation of the absorbent, by acidic components,
or by products of reaction of these acidic components
with the absorbent. For example, although aqueous
alkanolamine itself is not particularly corrosive toward
.
iron and steel equipment, it becomes highly corrosive
when there are dissolved CO2 and minor amounts of H2S
present, particularly when it is hot. To combat this
problem, various metal compounds have been used alone or in
combination with other compounds as corrosion inhibitors,
for example, compounds of arsenic, antimony, and vanadium.
While such metal compounds are effective corrosion inhibitors~
they have the disadvantages of low solubility in most
gas conditioning solutions and of relatively high toxicity.
18,313A~
- . ' .,: , : , . .
, . .
~V1~68'7
The latter property is particularly undesirable
since it affects both the handling of the solvent and
the disposal of waste material. ~hey are also ineffective
in the presence of H2S.
The problems of toxicity and corrosion described
above have been subs-tantially overcome by the present
invention, which is a composition for inhibiting corrosion .
of iron and steel by carbon dioxide and optionally a minor
quantity of hydrogen sulfide in gas conditioning solutions,
10 compri.sing an inhibiting concentration in said solu-tion
of a combination of one part by weight of a quaternary
pyridinium salt and (1) 0.001-10 parts of a thio compound
which is a water-soluble thiocyanate, a water-sol~lble -.
sulfide, or an organic thioamider or (2) 0.01-10 parts
of a lower alkylenepolyamine, a corresponding polyalkylene~
; polyamine, or a mixture thereof wherein the alkylene units
contain 2-3 carbon atoms. - .
Essentially any pyridinium salt which is sta~le
in the gas conditioning solution is operable in the .
~ 20 invention. Preferably, this salt.has the formula:
. lR ' ' ,
R' ~ ~ R' X ~,
R' ~ R' ~.
'
where R is an alkyl radical of 1-20 carbon atoms, a
benzyl radical, or an alkylated benzyl radical wherein
the,aromatic ring has one or more alkyl substituents
25 . totaling 1-20 carbon atoms~ each R' is a hydrogen atom
18,313A~F -2-
.
: , , '~` ':
, ' ' . '
lL6~37
or an alkyl radical of 1-6 carbon atoms, and X is any
convenient anionic radical such as halide, sulEate,
aceta-te, or nitrateO In the above general formula,
X is preferably a bromine or chlorine atom and most
preferably bromine. sest results are obtained when
at least one R' represents an alkyl radical and par- -
ticularly good inhibition has been found when the
pyridine ring has multiple alkyl substi-tuents.
Preferably, R is a higher alkyl radical of about 10-18
carbon atoms.
The thio eompound in -the inhibitor combination
is preferably a water-soluble thiocyana-te such as an
alkali metal thiocyanate or, most preferably, ammonium
thiocyanate. It can also be an organic thloamide and -
essentially any such compound is operable. This class
of compounds includes thiourea, a polythiourea, a - ~ -
hydrocarbon substituted derivative thereof, or a
thioamide having the formula:
,S, R"
A-C-N
R
; 20 wherein A is a hydrocarbon radieal o~ 1-12 carbon atoms
or a pyridyl radical and each R" is a hydrogen atom or
an alkyl radical of 1-8 earbon atoms. Thioamides such
as thiourea, 1~2-diethylthiourea, propylthiourea,
l,l-diphenylthiourea, thiocarbanilide, 1,2-dibutyl-
thiourea, dithiobiurea, thioacetamide, thionico-tinamide,
and thiobenzamide are representative o~ this class.
Water-soluble sulfides such as ammonium sulfide, an
alkali metal sulfide, or corresponding hydrosulEide
ineluding H2S are other operable thio compounds.
:
- ': '
18,313A-F _3_
..
- . . : , ,
``` ~
~0~ 87
While any significant quantity of the combination
of the pyridinium salt and the thio compound will provide
some degree of inhibition of corrosion, at least about 100
parts per million concentration of the combination in -the
gas conditioning solution is usually required to provide
practical protection. More than about 2,boo ppm of the
inhibitor combination usually provides little or no added
protection. Either the thio compound or the pyridinium
salt alone will provide no inhibition or only partial
inhibition. It appears that very little of the thio compound
is usually needed in the presence of the pyridinium salt,
however, concentrations as low as one part per million of
thio compound in the presence of 50-100 parts per million
of pyridinium salt having been found to give effective
- 15 inhibition in some cases. About the maximum degree of
inhibition obtainable with a particular combination is
usually found when the concentration of the thio compound
reaches a concentration of 10-100 parts per million.
Higher concentrations of this component appear to offer
-little or no added benefit under most conditions but may
help ~hen the quaternary salt concentration is at a
disproportionately higher level.
On the other hand, it has been found that at
least about 50 parts per million and preferably 100-1000
parts of the pyridinium salt is required to obtain
optimurn results. For each combination, a maximum degree
` of inhibition seems to occur at a particular level within
the preferred ranges described above and higher concentra-
tions of either component or of the combined components
:. :
13,313A-F`
' '
:
6~
provide slight added pro-tection, if any. In many cases,
higher concentra-tions seem to cause a slight decline in
the degree of inhibition after a maximum has been reached.
- The polyamine component includes ethylenediamine,
propylene diamine, the various polymeric forms of these such
as tetraethylenepentamine, hexaethylenehepta~ine
tripropylenetetramine, dipropylenetriamine, the higher
molecular weight compounds of the same type and also the
closely related polymers of ethylenimine and propylenimine
as well as mixtures of any of these including polyalkylene
polyamines containing mi~ed ethylene and propylene groups.
These straight chain and branched chain polyamines can have
molecular weights running as high as several hundred thousand.
The term polyalkylenepolyamine is used herein to mean all of
- 15 these polymeric forms and mixtures thereof. Polyethylene-
polyamines are preferred, particularly those having an
average molecular weight of about 100-1000.
~ While any significant quantity of the combination
- of the pyridinium salt and the polyamine will provide some
degree of inhibition of corrosion, at least about 100 parts
per million concenLration of the combination in the gas
conditioning solution is usually required to provide
practical protection. Either the polyamine or the pyridinium
salt alone will provide no inhibition or only partial in-
: ~ .
hibition. It appears that relatively little of the poly-
amine is usually needed in the presence of the pyridinium
salt, however, concen-trations as low as 50 parts per million
of polyamine in the presence of 50-100 parts per million of
pyridinium salt having been found to give effective inhibition
18,313A~ _5_
,, .: , ,, ~ , ' ' ,
..
,, , ,. , . , .. ~ ,
i,. . .... .. . .
~08~6~37
in some cases. About ~he maximum degree o~ inhibition
obtainable with a particular combination is usually found
when the concentration of the polyamine reaches a con-
centration of 50-500 parts per million. Higher concentra-
tions of this component appear to offer little or no added
benefit.
On the other hand, it has been found that at
least about 50 parts per million and preferably 100-1000
parts of the pyridinium salt is required to obtain optimum
results.
The present invention afEords effective
inhibition of iron and steel corrosion by sour gas ~ -
conditioning solutions containing dissolved CO2 and H2S
; using relatively low concentrations of an inhibitor combina-
tion which is easily handled and convenient to use.
A concentrate of the combined compounds when the -thio
compound is a thioamide or a sulfide can be made up
in aqueous alkanolamine, aqueous giycol, or lower
-~ ~ alkanol and this concentrate can be added to the gas
treating solvent as required to make up or to maintain
a desired concentration. Since thiocyanates tend to
react on standing with the quaternary salt to form a
difficultly soluble, less active product, these thio
compounds are best added separately to the gas treating
solution, thereby forming the combination in si-tu a-t
higher dilution.
When a polyamine is the co-inhibitor, any con~
centrate should contain about 0.01-10 parts of the polyamine
per part of pyridinium salt and a concentra-te containing
0.1-1 part by weight of polyamine per part of salt is most
preferred
18,313A~F ~6-
.
687
This inhibitor combination is particularly
useful in aqueous lower alkanolamine solutions known
as sour gas scrubbing solvents. Preferred lower
alkanolamines ca~ be defined as those having the formula:
~, R R
~ N-C-C-OH
R R
wherein R' and R" independen-tly represent hydrogen or
; -CR2CR2-OH and wherein each R may be hydrogen or an
~ alkyl radical of 1-2 carbon a-toms. Representative
,~ .
alkanolamines are ethanolamine, diethanolamine, tri-
-~ 10 ethanolamine, isopropanolamine, diisopropanolamine,
:.
`~ and N-methyldiethanolamine. Related alkanolamines
which are useful acidic gas absorbents are Methicol
(3-dimethylamino-1,2-propanediol) and diglycolamine
:;
J (2-(2-aminoethoxy)ethanol). Other gas treating ab-
lS ~ sorbents in which this inhibi-tor combination is effec-
tive include suLfolane (tetrahydrothiophene~ dioxide)
and aqueous potassium carbonate. These absorbents
- ;~ can be employed alone or in combinations of two or
more, usually in aqueous solution although the water
may be replaced partly or entirely by a glycol.
The inhibitor combination of this invention
. .
is also effective to inhibit corrosion of iron and ~
, ~ .
steel by a gas-treating solution containing both CO2 -
, ::
and ~2S when the ~l2S is present in the solution at
; 25 limited concentration, up to about 500 ppm, for example,
and preferably not more than about 150 ppm. The inhibitor
combination is thus of wider applicability than many
known inhibitors which are not effective in the presence
- of dissolved H2S. ~ ~
.,, . ' .
.' '' :.. ~' . :
', ::',, :,
18,313A-F _7_
... . . . .
- ,. .. ; . .. , .. . . , ,. . :
', ~ ' . , . , ' ' ' , , ' ' . ~ ' ' ' ' ', ' ' ', ~ .
:~, ., , , . . , ::
37
Testing Procedure
:
The corrosion of mild steel by aqueous alkanol-
amine solutions saturated with CO2 for 7 hours at 10-20C
was measured at elevated temperat~res and moderate
S pressure. Loosely capped bottles each containing 120
ml of test solution and a totally immersed 1 x 2.5
x 0.0625 inch coupon (2.54 cm. x 6.35 cm. x 0.16 cm.)
of mild steel were put in a modified pressure filter for a
` period of 16-18 hours, at 125C and 40 psig (2.8 kg./cm~2)
unless otherwise specified. The test solvent was 30%
; by weight aqueous ethanolamine unless o-therwise specified.
The steel coùpons were previously cleaned with 5N HCl by~
immersion for 30 minutes at room temperature, followed by a
soap and water wash, a water rinse, then an acetone rinsa
and air drying. At least two bottles of each trial solution
were tested in each experiment along with three bottles of
solution containing no lnhibitor which served as controls.
After testing, the same cleaning procedure was used except ~ ~
that the HCl treatment was 15 minutes with SN HCl inhibited -
with a commercial HCl inhibitor in order to remove any -
'' :
corrosion deposits. The corrosion rate and efflciency of
inhibition were calculated according to the following
formulas using the average weight loss of the test coupons:
Rate in mils/yr (cm./yr.j =
(0.025~) x 534 x mgs weight loss of coupon
(coupon density, g/cc)(coupon surface, sq in)
(6.45cm. /in. ~(hrs)
% Inhibition = -
Corrosion rate of blanks - rate of test coupons x 100
.. .. . . _ . ............. . _ _ .
corrosion rate of blanks
18,313A-F -8-
: . , .
687
Preparation of Qua-ternary Salts
The qua-ternary pyridinium salts used in the
inhibitor compositions were made by heating a mixture
of the pyridine compound with excess alkyl halide or
benzyl halide at 90C for two hours. The reaction
mixture was then cooled and the quaternary salt was
recovered as a solid or viscous liquid precipitate.
The inhibitor compositions were added to -the
. aqueous ethanolamine as a solution in a small amount
10 of 60% by weight aqueous ethylene glycol or isopropyl alcohol.
~ Example 1 -.
: The pyridinium quaternary salt used in these
tests was the reaction product of tetradecyl bromide . .
and high boiling alkylpyridine still bottoms (HAP).
These still bottoms were from processes for making various ~ .
lower alkyl substituted pyridines wherein most of the
components were pyridines having multiple lower alkyl ~
:. substituents, particularly methyl and ethyl groups. ~his :
~: mixed quaternary salt was tested in combination with ~
NH4SCN, thioacetamide, thiourea, thionicotinamide, and ; .
thioisonicotinamide at various concentrations as noted.
., ,
, ': '
'
'.', .
. ~ -.....
1~,313A-F -9- -
. . .
'
Thio Concentration, ppm by wt.
Compound Quat. Salt Thio Compound % Inhibition
N~I~SCN 100 10 82.5
100 25 86.8
500 25 91.6
500 50 93.9
Thioacetamide 100 25 88.3
-- 100 50 83.2
~ 500 50 89.5
.... _
Thiourea 100 50 72.5
, 500 50 77.6
_.. __ . . .. _ . _
Thionicotinamide 100 25 92.2
100 50 92.2
Thioisonieotin-
amide 100 25 92.2 -
; 100 S0 - 92.2 ~
: . .
`~ 15 Example ? ~: -
....
Combinations of thiourea with benzyl pyridinium
',~ ehloride and with dodeeylbenzyl alkylpyridinium ehloride
~ (made from the alkylpyridine still bottoms described in
,; . . .
Example 1) were -tested for inhibition as described
above. A eombination of dodecylbenzyl alkylpyridinium ~ -
ehloride with thioacetamide was also tested.
Pyridinium Coneentration, ppm by wt.
Chloride ~ ~O Inh~bition
. . .
- Benzyl 1000 none 11 1
1000 25 30 2
Dodeeylbenzyl 1000 none 66.6
1000 1 89.7
1000 5 90.3
.: :
Dodecylbenzyl 1000 1* 91.5
1000 5* 90.6
1000 25* 90.6
- * Thio compound was thioacetamide
- .
~ 18,313A-F -10-
- - .
.
Example 3
Quaternary salts made from various higher
alkyl bromides and alkylpyridine still bottoms were
tested as inhibitors with and without NH4SCN as in the
foregoing examples.
Pyridinium Concentration, ppm by wt
Bromide Quat. Sal-tNH SCN~ Inhibition --~
- -------- --4
Dodecyl 100 none 7.2
100 50 64.4
500 10073.1
:
Cetyl 100 none-34.4
100 50 59.7
500 10062.3
Octadecyl 100none -14.3
~- 100 50 43.8 -
500 10053.9 -
,, _ ..... . .. . . ..
Example 4
Quaternary salts made by reacting tetradecyl
bromide with different alkylpyridines were tested as
` inhibitors in combina-tion with NH4SCN by the procedure ~-
0 F~eviously
: . .
18~313A-F
.,
.
. , . :,, , , : .
, . .. . . .
Concentration, ppm by wt.
Alkylpyridine Quat. Salt NH4SCN ~ Inhibi-tion
2-methyl- 100 50 27.0
3-me-thyl- 1000 none 54.5
1000 50* 88.8
2-ethyl- 50 50 3.2
100 50 31.1 ~ -
:, ~
3-ethyl- 100 50 83.7
500 50 93.6
.
2,4-dimethyl- 100 50 83.9
' 500 5~ 8307
~' ..: '
, ,, , ,. . ,, ,.,_ __ ,, .
- 3,5-dimethyl- 100 50 60.8 ~
:
500 50 73.3
., .. _ ., .... - ------ . ,
5-ethyl-2-methyl- 100 50 82.5
500 50 90.9
., _ , ,, __~
3-ethyl-4-methyl- 100 50 88.1
~ 100 100 89.9
500 100 95.7
,
.. ...
2,4,6-trimethyl- 100 50 73.5
500 50 84.9
,
,, ., . . _ _ ,, . . . , , ,, .. , ., . _ . _
* Thio compound was thioace-tamide
18,3J3~-F -12-
,
, ' . '
. .
~3
61~7
E~ample 5
The quaternary salt of Example l (tetra~ecyl
alkylpyridinium bromide) was tested in combination
with N~4SCN as before excep-t for using 35~ by weight
aqueous etllanolamine. Blanks were also run for comparison.
Concentration, ppm by wt
Quat. Salt NH4SCN% Inhibition
100 none -24.2
lO00 ,none -36.9
.... _.
none lO0 - 8.4
10 none 500 -20.2
39.3
500 26.4 ~-
- - - :
lO0 25 88.5
lO0 50 94.5
lO0 500 92.3
~ . :. . . :
500 lO 87.4
500 50 92.6
500 lO0 96.4
500 500 92.0
, 20 lO00 25 8l.0
;` lO00 50 87.6
1000 lO0 89.2
lO00 500 89.5
... .
.: . ...
:: .
i
'~
. .
.
18,313~-F -13-
:, . :. -, - .: , ;: , : , . . . .. ..
: '-:, :., . ' , . ' .,, . . ,, '' . : , , :
. ,. , . . , ,. , , . ,: . :,
, ,. ".. . ..
E~ample 6 ~8~6~7
The same quaternary salt described in Examples
1 and 5 was tested as before in combination with
NH4SCN at various concentrations using 15% by weight
aqueous ethanolamine as the test sol~ent.
Concentration, p_m by wt.
; Quat. Salt NH4SCN % Inhibition
:' , '
68.3
91.9 ~ -
- . 50 500 95.9
. . .
100 10 96.4
100 50 95.8
: 100 500 96.2
~: 500 10 9~.2
500 50 93.3
500 500 9~.8
... ... . . .. _ _ . . _ . .
-~ : 1000 10 89.0
1000 50 87.6
1000 500 91.7
,
"' " ' ' , ,
,
, ' ' ' ;' ;~ ' '
,: .. .
; 18,313A-P -14- :
~ . ,.: .. .. ..
,.''.. ' ', .' .~.', ~'. "' ', . , , ' ' .
687
Examples 7-10
The quaternary salt describ~d in Examples 1
and 5-6 was tested in combination with NII4SCN as before
using various aqueous alkanolamine-containing solutions
as test solvent.
Concentration, ppm by wt. Corrosion
Quat._Salt. NH4SCNSolvent (mm./yr ) % Inhibition
70% TEA 10.1 ---
100 50 " 0.3 92.6
500 100 " 0.7 93.1
_ _ _ (0.02)
--- --- 50~ DEA 10.4 --- -
100 50 " 0.6 93
500 100 " i~o 90.4
(0.03)
--- --~ 60~ DEA2 27.1 --- -
500 50 ~ 1-1 96.1
, (o . 03?
-- _ :
--- --- Mixed 19.0 ---
100 --- " 2.6 86.5
500 ___ ~ (0 07) 89 4
100 50 " (i.65) 91 8
` 500 100 " ~i.5) 92.1
(0.04)
lTEA - Tr1ethanolam1ne, by weight
DEA = Diethanolamine, by weight
Mixed = 45% diisopropanolamine, 35% sulfolane
20~.water, by weiyht
' ~ .. ' .: '
~ ' ' ~'"'"'
' '~
18,313A-F -15-
:'. ',
-:. , - . , ' -, , ,.. , , ' , ' " , ': . ' ' ' ' . '
,'-':" ' ~' "'' ' ' ''"' ' ' ~ "'' '''' ' ' ''
6a~
Example 11
Combinations of tetradecyl alkylpryidinium
bromide and NH~SCN were tested in 30% by weight aqueous
ethanolamine saturated with CO2 and containing 100 ppm by
weight of sulfide ion added as ammonium sulfide under test
conditions otherwise as previously described.
Concentration, ppm
Qua-t. Salt NH~SCN % Inhibition
100 --- 76.5
500 ___ 94.1
100 50 76~6
500 50 89.2
100 100 77.1
500 100 93.3
;~ 15 In the above tests, the ammonium sulfide
present in the alkanolamine solution to simulate the
presence of H2S served as the thio compound and so
the quaternary salt was active even in the absence
`~ of NH4SCN.
Examples 12-17 -~
In the following examples, the quaternary salts
~ere prepared as in Examples 1-11 and the same test pro-
cedure was used, except that an H2S equivalent was added
to the aqueous alkanolamine. The H2S was added to the
CO2-saturated aqueous alkanolam;.ne as an amount of
aqueous (NH~)2S sufeicient to supply sulfide and hydro-
sulfide ions in.about the same concentrations as the
~1 listed.H2S concen-tration would provide. In Examples 12 to
14 the corrosion inhibition testing was done at 125C
: 30 in 30 percent by weight aqueous ethanolamine saturated :~.
with CO2 and containing the equivalent of, by weight,
100 ppm, 300 ppm, and 500 ppm H2S as (NH~)2S, respecti~ely.
~ '
18,313A-~ -16-
'
,~ .. . .. . .
,, . ~ . , . . '
' ' : . : .
08~6
Example 12
(100 ppm H2S)
:
Quat.Concentration, ppm by wt.
Salt Polyamine Quat. Salt Polyamine ~ Inhibition
TAPB(l) PEI_3(2) 100 -- 76.5
500 -- 9~.2
-- 100 64.3
-- 500 49.1 -
100 100 94.3 -
500 100 95.5
` 100 500 94.2 `-
-- _____________________ :
TAPB(l) E-100(3) -- 100 47.5 ` ` `
~~ 500 57-7
100 100 94.9
500 100 95.2
-~ (1) TAps = Tetradecyl bromide salt of polyalkylpyridines
in lower alkylated pyridine still bottoms (HAP).
These still bottoms were ~rom processes for making various
lower alkyl substituted pyridines wherein most of the
components were pyridines having multiple lower alkyl
substituents r particularly methyl and ethyl groups.
( ) PEI-3 = Polyethylenimine of about 300 average molecular
- weight. - -
(3) E-100 = Ethylenediamine plant still bottoms containing
85-90% pentaethylenehexamine and hexaethyleneheptamine with
some tetraethylenepentamine and small-amounts o~ branched
and cyclic isomers and derivatives.
Example 13
(300 ppm H~S~
'7 ` ' Quat. Concentration, ppm, by wt.
Salt Polyamine Quat. Sa~r-~-Polyamïne % Inhibi-tion
TAPB E-100 100 - 72.6
500 -- 86.0
i 1000 -- 83:7
-- 100 - 4.6
-- 500 10 1
100 100 90 8
500 100 88.7 `
100 500 gO.l
:~' ~, : '
,
. - .. . - . ,
~:
18,313A-F -17- `
.~ ~
.. . . .. . . .
' " ' ' ' ' ',
.
6~37
Example 14
(500 ppm H2S)
. , .
Quat. Concen-tration, ppm, by wt.
Sal-t Polyamine Quat. Sal-t Polyamine % Inhibi-tion
TAPB E-100 100 -- 57~1
500 _- 84.8
100 100 89.0
500 100 88.1
500 500 91.3
Examples 15-17 are essentially a repeat of
Examples 12-14 using 60 percent by weight aqueous diethanol-
amine as the éthanolamine solution. Equivalent amoun-ts of
~:
aqueous (NH4)2S were added as before to the CO2-sa-turated
alkanolamine to provide about the concentrations of sulfide
and hydrosulfide ions formed by the listed amounts of
~. 15 H2S .
Example 15
(100 ppm H2S)
.~ .
Quat. Concentration, ppm, by wt.
Salt Polyamine Quat. Salt Polyamine % Inhibi-tion
TAPB E-100 100 -- 92.8
~ ~ 500 -- 93.6
- 20 1000 -- 92.3
- -- 100 25.8
A; . 500 55.8
100 100 96.2
500 100 96.2
,
.
Example 16
(300 ppm H2S)
:. . .
Quat. Concentration, ppm! by ~t. _
Salt Polyamine Quat. Salt Polyamine ~ Inhibitio~
TAPB E-100 100 -- 88.6
5~0 -- 90.3
~- 10 0 ~9 . 1
-- 500 ~0.2
100 100 93.2
500 100 91.8
-- 100 500 92.6
18,313A-F -18-
. .. ... .
:. ~
. .
3fl6~7
Example 17
(500 ppm H2S)
Quat. Concentration, ppm, by wt.
Salt Polyamine Quat. Salt Polyamine % Inhibition
TAPs E-100 100 -- 8~.0
500 -~ 83.2 ~ -
1000 -- 84.0
-- 100 39.6
-- 500 46.3
-- 1000 27.6
100 100 86.6
500 100 85.5
Similar effective inhibition o~ corrosion is
found when the quaternary salt of the above examples
is replaced by the same amount of other pyridinium salts
as previously defined, for example, dodecylbenzyl 3-ethyl-
4-methylpyridinium chloride, dodecyl alkylpyridinium
bromide (made from HAP alkylpyridine still bottoms),
tetradecyl 3-ethylpyridinium bromide, and tetradecyl
trimethylpyridinium bromide. Similarly, closely comparable :
results are obtained when the polyamine component in
these examples is replaced by the same concentration ~
of polypropylenimine of 500 average molecular weight, -
triethylenetetramine, hexapropyleneheptamine, or other
such polyamine as defined above.
In the same way, ef~ective inhibition o~ ferrous
metal corrosion is also obtained when these quaternary
pyridinium salt-polyamine combinations are Inaintained at
the disclosed concentration in other sour yas conditioning
solutions such as previously described. For example,
aqueous or glycol-containing solutions o~ diethanolamine, ~ ~
.. , ~ ,.
~. , ' .~ '
.'' . ~ .
', '.-
''".
~' ' '
1~,313A-F -19-
~ . :
~''
~ ; ;
~0~;8~
N-me-thyldiethanolamine, diisopropanolamine, and mixtures
of these including mixtures with sulfolane and-other
known gas conditioning solvents, also aqueous potassium
carbonate are all pro-tected by these inhibitor combinations.
~ .
~', ~,. .
;' , ' '
'.
'
:~ ' ' ' ' '
-'"
~-'. .
.
- ' ' '
,;
18,313A-F -20- :
,', . . .
. . .
' . ' ' . , .
.
