CA1183838A

CA1183838A - Imidazoline based corrosion inhibitors which inhibit corrosion caused by co.sub.2 and h.sub.2s

Info

Publication number: CA1183838A
Application number: CA000397860A
Authority: CA
Inventors: Knut Oppenlaender; Karl Stork; Klaus Barthold
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1981-03-14
Filing date: 1982-03-08
Publication date: 1985-03-12
Also published as: EP0060455A1; NO157219C; DE3260316D1; DE3109827A1; NO820813L; NO157219B; EP0060455B1

Abstract

Abstract of the Invention The subject invention relates to corrosion inhibitors prepared by reacting certain imidazolines or precursors thereof with sulfur. The corrosion inhibitors are particularly useful in inhibiting corrosion of metal tanks caused by CO2 and H2S ("acid gas") during the trans-port and storage of crude oils.

Description

L ~ i ~.J

~3~38 IMIDAZOLINE BASED CORROSION INHIBITORS

Background of the Invention 1. Field of the Invention -The subject invention relates to corrosion inhibitors prepared by reacting certain imidazolines or precursors thereof with sulfur. The corrosion inhibitors are particularly useful in inhibiting the corroslon of metal tanks caused by CO2 and H2S ("acid gas") during the trans-port and storage of crude oils.

2. Description of the Prior Art _ _ .
It is known to inject a solution or dispersion of corrosion inhibitors into crude oil during oil recovery and during the transport or storage of oil so that a protective layer forms on the surfaces of the metal parts coming into contact with the oil. The crude oil emulsions usually contain saltwater and in many cases, depending upon the origin of the oil, H2S and CO2 which have a pronounced corrosive effect. The corrosion inhihitors to be used for this purpose should be soluble in oil and should at least be dispersihle in saltwater so that they can have an optimum effect.

~9 ~:~333838 German Published Application 2,846,979 describes corrosion inhibitors for this purpose which consist of an imidazoline salt, an oil-soluble solvent for the imidazoline salt, and a hydrocarbon oil. The problem with these inhibito~, however, is that the imidaæoline salts described in the referenced literature do not sufficiently suppress t'ne corrosion caused by H2S and CO2, which are often present in the crude oil which is essentially a water-in-oil emulsion, particularly a saltwater-in-oil emulsion. In addition to this, the use of imidazolines under these circumstdnces is complicated because they must be used together with specific solvents. Moreover, the costs of the hydrocarbon oil is high.
U. S. Patent 3,062,612 describes a process for preventing the corrosion of iron from acid corrosion whereby a finely distributed sulfur together with, among other things, long chained fatty acids, aliphatic amines and/or quaternary ammonium salts of these amines, imidazolines, or organic sulfides are added to the corroding medium.
~lowever, thls patent relates to a different problem than the subject invention, (it is concerned with corrosion protec-tion agents used ~or aqueous acid solutions and not for water-in-oil emulsions where the question of solubility is of significant importance) and only ethoxystearylimidazoline is mentioned by way of example in addition to other

3~33~

amines. The imidazoline precursors which are used in accordance with the subject invention to prepare the corroslon inhibitors are not described anywhere in this patent~ Furthermore, it has been shown that a mixture of elementary sulfur and ethoxystearylimidazoline brings about totally unsatis~actory results with respect to corrosion protection when used according to this invention in an H2S containing saltwater-in-oil emulsion.
Summary of the Invention The subject invention relates to corrosion inhibitors which are the reaction product of (A) a compound selected from the group consisting of 1. an imidazoline or salt thereof having the following structural formula ~ N-CH2 N-CH2 (I) 2. a precursor thereof having the following structural formula:

'' H
Rl-c-N-cH2cH2NH-cH2cH2x (Ia) ~L83~3~

wherein R is a C6 to C22~ preferably C8 to C17, alkyl or alkenyl radical;
X is OH, IIH2, or [NH3]~[0-P-OR2] ~ ; and oR2 R is a C4 to C18, preferably C7 to C17, alkyl radical, and (B) elementary sulfur;
wherein (A) and (B) are reacted at 100C to 200C within lQ 1 to 3 hours in a weight ratio of (A) to (B) of 100:1 to 2:1.
The corrosion inhibitors axe particularly useful for inhibiting corrosion caused by the CO2 and H2S in crude oil stored in metal containers. Crude oil is essentially an oil-in-water emulsion, more specifically a saltwater~in~oil em~llsion. The subject inhibitors can be metered in a simple manner.
Description of the Preferred Embodiment ., . . _ _ The preparation of the irnidazoline derivatives is part of the current state of the art and does not require any detailed explanation. Normally acids having the Eormula RlCOOH are reacted with diethylenetriamine or aminoethylethanolamine at approximately 70C to 130C which 3~351 initially results in the acid amide of formula (Ia) which can be used by itself. Rl in this case has the meaning identified for formula (I) previously set forth.
Following this process the product is further reacted at approximately 190C to 250C resulting in the production of imidazoline which can be converted into the ammonium salt by further reaction with the dialkylorthophos-phoric ester after the acid has been reacted with diethyl-enetriamine in the first stage.
Acids having the formula RlCOOH which can be used include 2-ethylhexanoic acid, nonanoic acid, oleic acid, stearic acid, lauric acid, elaidic acid as well as mixtures of natural fatty acids such as coconut or tallow fatty acid.
Orthophosphoric diesters which can be used include those which are derived from amyl alcohol, n-hexanol, n-heptanol, n-octanol, 2-ethylhexanol, nonanols, decanols and isotridecanol, stearyl alcohol, oleic alcohol as well as the Cg/Cll- and Cl3/Cl5-fractions originating from the oxosynthesis The C~/Cl0 Cl0/C12 and C14/ 16 mixtures derived from the Ziegler synthesis may also be used.
Particularly useful in preparing the subject corrosion inhibitors are imiclazolines or imidazolinium phosphate ester salts which are derived from the Cl2 to C20-carboxylic acil~s, for instance, compounds having the formulae il3~33~

C17H33-C ~ l C17H33-C ~ ¦ and CH -CH OH , 2 2 2 2 2 , ,~ U-CH2 1 ~ / OCaH17 as well as the corresponding C17H35 derivativesO
The imidazoline derivatives and/or their pre-cursors (A~ are subsequently mixed with sulfur (B) which should advantageously be present in its colloidal form (that is, as sublimated sulfur) and are subsequently brouyht to reaction by heating to 100C to 200C for 1 to 3 hours. The weight ratio of A:B is 100:1 to 2:1, preferably 100:1 to

4:1.
The resultant compositions which can be added to the water-in-oil emulsions in free form provide optimum protection against H2S and CO2 corrosion. Depending upon the origin and/or the compositions of the crude oil emul-sion, these compositions are used in quantities of 50 to 1000 ppm relative to the weight of the emulsion.
The following examples more specifically explain the invention, but are not intended to limit the scope of its application.

~3~3~

Examples In the ~ollowing examples the effectiveness of the corrosion inhibitors was tested as follows:
Iron sheet metal having dimensions of 130 mm x 10 mm x 1 mm was selected as test material~ These sheet metal strips were sanded, degreased with toluene, and weighed. Test gasoline, containing in emulsified form, saltwater with 3 percent NaCl, relative to the water, was used as a test medium. The emulsion contained 50 percent by weight of saltwater and was saturated with H2S and CO2~
To the emulsion was added 250 ppm of inhibitor relative to the weight of the emulsion.
The degreased and weighed sheet metal strips were subsequently introduced into tAe emulsicns and were sub-jected to mechanical movement (40 rpm imparted by a shaft turning the test vessels) at 80C for 16 hours.
The strips of test metal were then cleaned with~an inhibited acid, were degreased, and were weighed after drying in order to determine the weight loss. The results were evaluated and compared with blank values (emulsions without the inhibitor added).
The results are shown in the following tables. In addition to the blank values, these tables also show the results obtained with imidazolines alone (without sulfur) and with etho~ystearylimidazoline in accordance with U. S.
Patent 3,062,612.

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The compounds used as component A in Examples 1 to 10 had the following structural formula and were used ln amounts of 250 ppm:

R -C
N-CH

~3~33~3 TABLE I (Examples 1-10j Amount Eroded F.xample Rl X Percent S* in m~

1 Blank Sample - - 109.9 8 17 NH2 Pitting 17 33 OH o ~ 81.3 (pittin~) 4 i-C8H17 NH2 1/5/10 37.2/33.6/32.2 17 33 NH2 5/20 30.0/27.3 17 3 OH 1/5/10 32.3/24.0/23.5 17 35 NH2 1/5 38.4/33/9 17 33 OH 15/20/30 25.6/21.7/19.3 8 17 ~H2 15/30 32.8/32.5 Ethoxy-stearyl-10 imidazoline - 10/20** 68.5/57.3 ___ * Incorporated by heatin~ with imidazoline derivative -to 150C within 2 hours (clear solutions) **In accordance with U. S. Patent 3,062,612 was added and mixed as colloidal aqueous solution 31~33~

The compounds used as component A in Examples 11 to 19 had the following structural formula and were used in amounts oE 250 ppm:

R -c-~lH-cH2cH2-ME~-c~2cH2-x -TABLE II (Examples 11-19) Amount Eroded Example Rl X Per oent S* in mg 11 Blank Sample -- -~ 114.9 12 C17H33 OH 5/10/20 49.6/36.0/28.4 13 C12H35 OH 5/10/20 43.6/24.9/24.8 14 Tallcw fatty aIkyl OH 5/10/30 50.6/26.3/23.5 Tallow fatty alkyl NH2 1/5/10 31.5/28.1/27.8 16 Colza oil fatty alkyl OH 5/10/50 28.5/25.5/26.2 17 Colza oil fatty aIkyl ~12 1/5/10 33.2/31.5/28.5 18 C17H33 NH21/5/10 29.4/27.0/25.5 19 C17H33 N~l2 0 95.8 * Incorporated as set forth in Table I

8~3133~3 The compounds used as component A in Examples 20 to 25 had the following structural formula and were used in amount of 200 ppm.

C 2CH2N ~ < O-CE~H17¦

TABLE III (Examples 20-25) Example Rl Percent S* Amount Eroded Blank Sample -~ 114.3 21 i-C8H17 112.5 22 C17~33 o 113.1 23 C8H17 1/5/10 33. 0/29. 9/32.0 24 C17H33 1/5/30 28.7/25.0/24.2 C17H35 1/5/50 29.4/28.5/26.3 Examples 1 to 25 show the effectiveness of the corrosion inhibitors described and used in accordance with present invention.

*Incorporated in accordance with the data put forth in Table I

- 11 ~
.

Claims

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A corrosion inhibitor comprising the reaction product of (A) a compound selected from the group consisting of (1) an imidazoline or salt thereof having the following structural formula (I) (2) a precursor thereof having the following structural formula:

(Ia) wherein R1 is a C6 to C22 alkyl or alkenyl radical;
X is OH, NH2, or R2 is a C4 to C18 alkyl radical; and (B) elementary sulfur;
wherein (A) and (B) are reacted at 100°C to 200°C within 1 to 3 hours in a weight ratio of (A) to (B) of 100:1 to 2:1.

2. The corrosion inhibitor of claim 1 wherein R1 is C8H17 or C17H33.

3. The corrosion inhibitor of claim 2 wherein X
is OH or NH2.

4. A process for inhibiting the corrosion of metal caused by H2S and CO2 in oil-in-water emulsions containing H2S and/or CO2 comprising adding a corrosion inhibitor prepared in accordance with claim 1 to an oil-in-water emulsion.

5. The process of claim 4 wherein the oil-in-water emulsion is a saltwater-in-oil emulsion.

6. The process of claim 4 or 5 wherein the amount of corrosion inhibitor added to the oil-in-water emulsion is from 50 to 1000 ppm by weight based upon the weight of said emulsion.

7. A corrosion inhibitor comprising the reaction product of (A) a compound selected from the group consisting of (1) an imidazoline having the following structural formula (I) (2) a precursor thereof having the following structural formula:

(Ia) wherein R1 is a C6 to C22 alkyl or alkenyl radical;
X is OH, NH2, or ; and R2 is a C4 to C18 alkyl radical; and (B) elementary sulfur;
wherein (A) and (B) are reacted at 100°C to 200°C within 1 to 3 hours in a weight ratio of (A) to (B) of 100:1 to 2:1.

8. The corrosion inhibitor of claim 7 wherein R1 is C8H17 or C17H33.

9. The corrosion inhibitor of claim 8 wherein X
is OH or NH2

10. A process for inhibiting the corrosion of metal caused by H2S and CO2 in oil-in water emulsions containing H2S and/or CO2 comprising adding a corrosion inhibitor prepared in accordance with claim 7 to an oil-in-water emulsion.

11. The process of claim 10 wherein the oil-in-water emulsion is a saltwater-in-oil emulsion.

12. The process of claim 10 or 11 wherein the amount of corrosion inhibitor added to the oil-in-water emulsion is from 50 to 1000 ppm by weight based upon the weight of said emulsion.