GB2394224A - Zwitterionic water soluble quartenized imidazole compound as a corrosion inhibitor - Google Patents

Abstract

A zwitterionic water soluble imidazole compound - 3-(2-(propylidine TOFA/DETA imidazolium)) propionate - is useful as a corrosion inhibitor of ferrous metals.

Description

WITTERIONIC WATER-SOLUBLE SUBSTITUTED IMINE CORROSION INHIBITORS

This invention concerns z\vitterionic water-soluble imine corrosion inhibitors, compositions comprising the corrosion inhibitors and a method of inhibiting corrosion of ferrous metal surfaces in contact with corrosive fluids.

BACKGROUND OF TlIE INVENTION

This invention relates to a method for inhibiting the corrosion of ferrous metals.

More particularly, this invention concerns a method for inhibiting corrosion of a ferrous 15 metal subjected to aqueous acid environments. In narrower aspects, the present invention relates to an acidizing process for the removal of calcareous scale Connations from a ferrous metal surface whereby corrosive attack of the metal substrate is inhibited.

In many industrial practices, the need to contact ferrous metal surfaces with strong acidic agents constantly arises. Particularly under numerous industrial circumstances 20 equipment fabricated of ferrous metals such as boilers often accumulate scale formations which must be periodically removed in order to maintain the efficiency of the equipment involved. For example, it is common within the petroleum industry to utilize heater tubes in contact with crude oil containing emulsified aqueous solutions of inorganic salts, particularly those of calcium, in order to effect separation of oil and water. The briny 25 solution, upon contacting the heated metallic surfaces, deposits a substantial portion of mineral content upon said surfaces in a forth of insoluble calcareous formations.

Consequently, in order to maintain reasonable efficiency of the heaters and to obviate burning out of the heater tubes it is necessary to remove the scale formations periodically that have formed. The latter is but one example of many of such operations in the 30 petroleum field which requires frequent acidizing treatment of various pieces of

equipment made of iron or a ferrous alloy. Also in many chemical processes it is necessary to store or transport acids, such as the common mineral acids, \vlhile in contact with ferrous metals. Aceordirigly it can be seen that the practical situations necessitating the minimizing or obviating of the corrosive ef't'ect acidic materials, especially those of' 5 mineral origin, uporI ferrous metal surfaces fire legion.

I lo\\-inGiucetl locali7.ctl corrosion (I IL(2) is a rcst,.lt of high shear conditions present in flow lines. 'I'he amount of'eorrosiorI that occurs is depentlerlt on a variety of' factors including the corrosiveness of the tluitf flowing througl, tle lines, the metallurgy of the line and the ability of atided corrosion inhibitors to maintain adhesion to the 10 interior of the line.

T'he ability of atIdetl corrosion inhibitors to maintain adhesion to the interior of the line depends on both the eherrIieal adhesive properties -, f the inhibitor anti the shear stress conditions which exist inside the line. A number of'roducts have shown promise as shear-resistant corrosion inhibitors. Included among, the corrosion inhibitors are arllitles 15 and quatemized amines arItl amitle Ermine salts.

Many nitrogen-contairIing corrosion inhibitors are known. Among them are: morpholine, disclosed in U.. Patent No 3,649,167; imicla;.,lirles in U.S. Patent No. 3,197,403; amidic acids in U.S. Patent No. 2,742,498; bisamitles in U.S. Patent No. 4,344,861; amines in U.S. Patent Otis. 5,21 1, 8,40 and 5,714,664; amides in U.S. Patent 20 No. 5,556,575; and earbohydra;.ides in U.S. Patent Nos. 5,078,966. The reaction of acrylic acid with substituted imiclazolines to form variotrs amine derivative corrosion inhibitors has been disclosed in U.S. I\atent Nos. 5,300,235; 5, 322,630; 5,322,640 and 5,427,999.

Schif'f bases have been disclosed as corrosion inhibitors in IFS. PatcrIt No. 25 5, 1 47,567, in Materials Chemistry and PHYSICS, 39 ( 1 995) 209-2 13 and in (corrosion Science, 2(, (1986) 827-X37. Moreover, imincs have also been disclosed as corrosion inhibitors, and as additives to corrosion, inhibitor formulations. I or example, imines have been disclosed as useful in conjunction with aromatic triazoles to enhance corrosion inhibition in U.S. Patent No. 4,642,22 1; and imine dispersants have been utilized to 30 enhance the activity of trithiones as CO2 corrosion inhibitors in lap 0 275 651. Imines

have been disclosed as corrosion inhibitors in U.S. Patent No. 4,490,293; JP 74021 024B and SU 31831SA.

SUMMARY OF TI IE INVEN I ION

r I have discovered certain novel z\vitterionc imirie compositions \vhich inhibit corrosion of ferrous metal surfaces in contact with acidic tiuids which contain water Aeeordingly, in its principal aspect, this invention is directed to a zwitterionic \vater soluble imine of fonnula: R3 1'. R2

(CH2)p Z wherein R' is selected from heterocyclyl, heteroaryl, aryl, arylalkyl, eycloalkyl and 1 5 alkyl, R2 is sheeted from alkyl, alkenyl, arninualkyl, diamirioalkyl, hydroxyalkyl, alkoxyalkyl, thioalkyl, alkylthioalkyl and arylalkyl; R3 is selected from hydrogen and lower alkyl, or R' and R3 taken together form a cyeloalkyl, 20 pis2, 3,4Or5; and Z iS CO2, OC02, GOT, 0803, PO3- fir OPO3-.

DETAILED DESCRIPTION Old Tl-IE INVENTION

25 "Alkyl" means a monovalent group derived from a straight or branched chain saturated hydrocarbon by the removal of a single hydrogen atom Preferred alkyls are straight chain C6-C24 alkyl groups More preferred alkyls are straight chain C'2-C24 alkyl

groups. Representative alkyls are the hydrocarbon residues of caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid and stearic acid.

"Lower alkyl" means a (2-C2s straight or branched chain alkyl group.

Representative lower alkyl include methyl, ethyl, propyl, isopropyl, butyl, and the like.

5 "Alkylene" means a clivalent group derived from an alkyl as defined heroin by the removal of two hydrogen atoms. Representative alkylene include methylene, ethylene, propylene, and the like.

"AIkenyl" means a monovalent group derived from a hydrocarbon containing at least one carbon-carbon double bond by the removal of a single hydrogen atom.

I O Preferred alkenyls are straight chain ('6-C20 alkenyl groups containing I, 2 or 3 double bonds. More preferred alkenyls are straight chain C''6-(12o alkenyl groups containing 1, 2 or 3 double bonds. Still more preferred alkenyls are the hydrocarbon residues of palmitoleic acid, oleic acid, linoleic acid and linolenic acid.

"ALlkoxy" and "alkoxyl" mean a lower alkyl-()- group. Representative alkoxy 15 groups include methoxy, ethuxy' propoxy, butoxy, and the like.

"AIkoxyalkyl" means a lower alkyl-(:)-alkylene group where the lower alkyl is defined herein and the alkylene is a straight chain alkylenyl radical of two to about five carbon atoms. Representative alkoxyalkyl groups include ethuxyethyl, propoxyethyl, butoxyethyl, and the like.

20 "FIydroxyalkyl" means a straight chain lower alkyl of two to about 5 carbon atoms substituted with hydroxy. Representative hydroxyalkyl groups include 2-hydroxyethyl, 3-hydroxypropyl, and the like.

"Thioalkyl" means a straight chain lower alkyl of two to about 5 carbon atoms substituted with -SIN. Representative thioalkyl groups include 2thioethyl, 3-thiopropyl, 25 and the like.

"AIkylthioalkyl" means a lower alkyl-S-alkylene- group where the lower alkyl is defined herein and the alkylene is a straight chain alky}enyl radical of two to about f ive carbon atoms. Representative alkylthioalkyl groups inchide methylthioet}lyl, ethylthioethyl, methylthiopropyl, and the like.

"Aminoalkyl" means a Y,NH-(CH2)n- group where n is 2 or 3 and Yl is C',C3O alkyl or C2-CO alkenyl. Preferred alkyl groups are Cl-C, alkyl. More preferred alkyl groups are ('I-C5 alkyl. Preferred alLenyl groups are the hydrocarbon residues of palmitoleic acid, oleic acid, linoleic acid and linolenic acid.

5 "Diaminoalkyl" means a Y'NH-(C'H2)n-Nll-(C'Tl2)m- group wherein Y. and n tare defined herein and m is 2 or 3. I'referTed alkyl groups are (I-C,l alkyl. More preferred alkyl groups arc Cl-(2s alkyl. I'reterred alkenyl groups are the hydrocarbon residues of palmitoleic acid, oleic acid, linoleic acid ancl linolenic acid.

"Cycloalkyl" means a non-aromatic monocyclic ring system of about 5 to about 6 10 carbon atoms. I he cycloalkyl is optionally substituted with alkyl. Cl-C30 alkyl groups are preferred (2I-Cll alkyl groups are more preferred and C'-5 alkyl groups are still more preferred. Representative cyckalkyl groups include cyclopentyl, cyclohexyl, cycloheptyl, and the like.

"Aryl" means an aromatic monocyclic or multicyclic ring system of about 6 to 15 about 14 carbon atoms Phe aryl is optionally substituted with alkyl. Reprcsentative aryl groups include phenyl car naplltllyl, ant}lracyl, and the like.

"Arylalkyl" means an aryl-alkylenc- group where aryl and alkylene are defined herein. A preferTecl aryl group is phenyl. C,-('O alkylene groups are prefeTcd, C'l-('ll alkylene groups are more preferred and Cl-C5 alkylene groups are still more preferred.

20 "Heteroaryl" means an aromatic monocyclic or multicyclic ring system of about 5 to about 10 ring atoms, in which one or more of the atoms in the ring system is/are element(s) other than carbon, for example nitrogen, oxygen or sulfur. Representative heteroaryl groups include furanyl, thiophenyl, pyridyl, oxa%olyl, pyrTolyl, benzofuryl, benzothiophenyl, and the like.

25 "lleterocyclyl" means a non-aromatic saturated monocyclic ring system of about 5 to about 6 ring atoms in which one or more of the atoms in the ring system is/are element(s) other than carbon, for example nitrogen, oxygen or sulfur. Representative heterocyclyls include, pyrrolidinyl, tctrahydrc-,furanyl, tetrahydrothiop}lenyl, tetrahydropyranyl, and the like.

Representative Nvater-soluble zwitterionic imines according to this invention include, but are not limited to W / c'll2(C'}42)7CH--Cl I(C}42) 713 Now >I ()Q

O 5 3-(benzylidene-N-oleyliminium) propionate, 0 / CEl2(C I 12)7C H=C'H(C'l-l2)7ctl3 (I) // O 3 -(cyclohexyl idenc-N-oleyl irninium) propionate, BIND CIl2(CH2)7Cil=Cil((2H2)7('[3 (I) /o 10 O 3-(propylidencN-oleyliminium) propionate, I / Cil2(t't]2)7CtI=(- I(CH2)7C} 13 \ o

i 3-(isopropylidene-N-oleyliminium) propionate /W / ( l T2(( l l2)7Cl l-('l l(Cl 12)7Cl l3 o> 3 -(furyl idene-N-oleyl iminium) propi-,nate, s : \ C H2(CI 12)7( l l=Ctl(CT-2)7T l3 \ 0/o 3-(henzylidene-N-(oleylaminopr<, pyl) iminium) propionate, /\ j\ / ( l 12(CI 12)71 I=c f l(12)7ll3 Now I I \ (a) /o o 10 3-(cyclohexylidenc-N-(oleylaminopropyl) iminium) propionate, \/ N/\/ \ / ( l-l2(c li2)7c l l=c l(cl 12)7cl ll }I \ o/0 3-(propylidencN-(oleylaminopropyl) iminium) propion.4t: and

i /N(3 \i\ / Cil2(Ct]2)7Cll=CIl(CEl2)7CH I-1 o / o 3-(isopropylidene-N(oleylaminopropyl) iminium) propionate.

In a preferred aspect of this invention, Z is CO2-.

r In another preferred aspect -,f this invention, R' is selected from phenyl, cyclohexyl, n-propyl, isopropyl, dodecyl and furanyl.

In another preferred aspect of this invention, R2 is propyl oleyl amine or C,2-(2 10 straight-cilaill alkyl.

In another aspect, this invcilti<-,n is directed to a method of inhibiting corrosion in metallic floNv lines for carrying fluids comprising adding to the fluids an effective amount of a water-soluble zwitterionic imine of formula R3 R,1() N R2

(CH2)p-Z wherein K, is selected from hetcrocyclyl, hcteroaryl, aryl, arylalkyl, cycloalkyl and 20 alkyl; R2 is selected from alkyl, alkenyl, aminoalkyl, diaminoalkyl, hydroxyalkyl, alkoxyalkyl, thic,alkyl, alkylthioalkyl and arylalkyl;

R3 iS selected from hydrogen and lower alkyl, or R' and Rat taken together form a eycloalkyl, p is 2, 3, 4 or 5; and 7, is 0'02, OCEAN, 8() 3, 08()3,10- or (.)PO3-.

s I'he corrosion inhibitor may be addeti to the fluid in the tome ol'a sohtion or dispersion in water or an organic solvent. Examples of suitable solvents are aICOhOIS such as methanol, etiranol. isoprupanol, isobutanol, secondary hutanol, glycols and aliphatic and aromatic hydrocarbons.

10'I'he amount of active ingredient in the corrosion inhibitor formulation required to achieve sufficient corrosion protection varies with the system in \vhich it is used Methods for monitoring the severity of eonrosion in different systems are well known, and may be used to decide the effective amount of active ingretlieut required in a particular situations The compounds may be used to impart the property of'corrosion I Sinhibition to a exposition for use hi an oil or gas filed application and which may have one or more functions other than corrosion inhibition, e.g. scale inhibition I-he imines deserted herein have been shown to be extremely effective for inhibiting mild steel corrosion, in hydrocarbon, oil/brine mixtures and aqueous systems under a variety of' cant itions. 'I'he inhibitor is most successful on sweet systems, or 20 systems having a high C2O2 content. I lowever, use of the compound in systems having sour conditions (high I 12S concentration) is also acceptable. Although fluid content of the flow lines may vary, the inhibitor may he used in a variety of environments. (Gil cuts in the field can range Prom less than 1% (oil fieltl) to 100% (refinery) oil, while the nature of

the water can range from ()-30O,000 ppm ADS (total dissolved solids). In addition, t}liS 25 material would not only be useful in the large t iameter flow lines (I.DF's) of from about I inch to about 4 feet in diameter, hut woult also work in small gathering lines, small flow lines and headers. In the preferred methoti, the imine inhibitor is adtled at any point in the flow line upflow from the point at W}liC}1 CorrOsit?T1 prevention is desired.

IT1 practice, the imine inhibitor is preferably added to the flow line continuously to 3() maintain a corrosion inhibiting t ose of from about 0. 01 to about 5,000 ppm. More

preferably the corrosion inhibiting dose is from about 1 to about 500 ppm. In the most preferred embodiment of the invention the corrosion inhibiting dose is from about I to about 250 ppm. Although a most preferred use of the compound in the claimed method is for metallic flow lines comprising mild steel it is believed that the inhibitor is also 5 effective in inhibiting the corrosion in other types -'t'metalhrgy. 1, certain cases hatch treatments are the Acted of'ch<-'ice for application of the imi',c inhibitor.

Dosage rates for hatch treatments range from about ().1 to about 50 ()()0 pun.

In a preferred aspect of this invention the flow rate of the flow line in which the inhibitor is used is between O to 65 feet per second. A more preferred flow rate is 10 between 0 to 40 feet per second. still more preferred flow rate is between () and 35 feet per SCCOlid. In some cases the imine may he formulated in water in order to facilitate addition to a flow line.

I'he imine may be used alone or in combination witl1 other compounds. Typical formulations of the imire may use alcohols or glycols as pour point depressants or 15 slrfactants such as ethoxylated nonylphenols and/or ethoxylated amines as wetting agents or additives for dispersing the Irvine into the stream into which it is acided.

I'ypical alcohols are C''-C'; linear or branched alkyl Broths and are used as pour point depressants. Useftrl gIycols include ethylene and propylene glycols and are also used as pour point depressants.

20 Surfactants utilized should be water soluble and allow the product to better wet the surface of the flow line where corrosion may take place. Water soluble surf'actants utilized may be non-ionic cationic or anionic and will generally have a hydrophilic lipophilic balance (IILB) value of about 1. Oil soluble surf'actants may be utilized if it is desired to disperse the imine composition into a hydrocarbon fluid. Oil soluble 25 surfactants may he non-ionic cationic or anionic. Phese surf;ackants typically have an IlLB value less than 7.

()ther compounds which may also be blended with the imine are Lluatcrnary amines such as fatty cyclic or aromatic amines quaterniz.ed with lower alkyl halides or benzyl chloride and certain amides. In addition formulations hcluding the imine 30 inhibitor may include filming agents such as p-toluene sulfonic acid and dodecylbenzene 1 0

( sulfonic acid. The corrosion inhibitor may also contain the materials which are typically included in corrosion inhibiting compositions e.g. scale inhibitors and/or surfactants. In some instances, it may be desirable to include a hiocide in the composition.

Accorclingly, in another aspect, this invention is directed to a composition 5 comprising: a) a z.witterionic water-solohle Zinc of hnnula: R3 1'. R2

(CH2)p-Z 1 0 wherein 1' is selected from heterucyclyl, heteroaryl, aryl, arylalkyl, cyckalkyl and alkyl; R2 is selected from alkyl, alkenyl, aminoalkyl, diaminoalkyl, hydr,xyalkyl, alkoxyalkyl, thioalkyl, alkylthioalkyl and arylalkyl; I 5 13 is selected from hydrogen and flower alkyl, or R' and Kit taken together form a cycloalkyl, p is 2, 3, 4 or 5; 7, is CO2-, OCO2-, SOT, OLSON-, PO3- or OPO3-, 20 b) a water soluble surfactant, and e) water. In a preferred aspect of this invention, the surfactant is selected from ethoxylated 25 alkyl amine and ethoxylated nonylpPenol.

In another preferred aspect of this invention, the composition further comprises a pour point depressant selected from alcohols and glycols.

In another preferred aspect of this invention, the composition further comprises a a co-inhibitor selected from amides, quatenized amines and amide amine salts.

5 In another preferred aspect of this invention, the composition further comprises a a filmhig agent selected from p-t'luenesulfonie acid and doclecylbenzencsulf<'nic acid.

In a more preferred aspect, this invention is directed k-, a composition comprising: a) a zwitterionie water-soluble imine of formula: R3 R,1()N 2 o oC) wherein R' is selected from heterocyelyl, heteroaryl, aryl, arylalkyl, eyeloalkyl and 1 5 alkyl; R2 is selected trom alkyl, alkenyl, aminoalkyl, diaminoalkyl, hydroxyalkyl, alkoxyalkyl, thioalkyl, alkylthioalkyl and arylalkyl; and R3 is selected froth hydrogen and lower alkyl, or R' and R4 taken together 20 form a cycloalkyl, b) a watersoluble surfaetant selected from the group consisting ot. ethoxylated alkyl amine and ethoxylated nonylphenol; 25 c) a pour point depressant selected from the group consisting of: alcohols and glycols; 1.2

( d) a co-inhibitor selected from the group consisting of: amicles, quaternizecl amines and amide amine salts; e) a filming agent selected l'rom the group consisting of: p-tohene sullonie avid and 5 dodeeylben:F. ene sttil'onie aeicl: and water. A representative composition aeeorcling to this invention is prepared by blending 10 tile following ingreclieuts into a homogeneous mixture. A preferred order of aldition is as follows: a) imine, b) methanol or isopropariol, e) alkyl pyricline benzyl ehl,ridc quatemary salt wherein the alkyl group is a methyl, ethyl or clisubstituteci group, ethoxylate alkyl having a certain Carbon length of Prom about C',0 to about ('NO and having 20 moles of'ethylene oxide per mole of amine, water and p-toluene sulkrlie aeicl. 'I'he 15 order of addition is not Critical to the invention as long as the resmelting mixture is homc-,gerleous. A representative composition is as follows: Compound /0 by wei}lt water I O-G() 20 methanol 5-30 isopropanol 5-30 ptolucne sulf'onic acid 0-5 ethoxylated alkyl amine surfaetant 2-15 imine corrosion inhibitor 5-50 25 alkyl pyricline benzyl ehkricie goat 0-15 Tlie inhibitor formulation may be used in a variety of petroleum operations in the gas and oil inclustry. It Can be used in primary, secondary and tertiary oil recovery and be adtieci in known manner. Another technique is primary oil recovery where they Can be used is the squeeze treating technique, whereby they are injected under pressure into the 30 producing formation, are acisorhet3 onto the strata and ahsorbeci as the fluids arc producccl.

1 3

They can further be added in the water flooding operations of secondary oil recovery as well as be added to pipeiincs, transmission lines anti refinery units. 'I'hey may also be used to inhibit acid solution in well acidizing operations.

I'he following; examplt s are presented to describe prefer-red cmbodimcuts and 5 utilities of the invention anti arc not meant to limit the invention unless otherwise stated in the claims appcoded heretic.

F.xam>le 1 I'he zwitterionic Irvine corrosion inhibitors of'thc instant invention arc the result 10 of Michael addition of acrylic acid to various imines under standard conditions to form the zwitterions. In a typical procedure, 0.1 mol of imine (prepared by combining ar1 aldehydc or ketone with a primary amine in the standard manner) was placed in a round bottom 4-neck flask equipped witl1 a stirrer. thermocouple and addition funnel. 'ho the imine was adtied (). I mol of a commercial grade of acrylic acid (available from 11 of 15 Parsippany, New Jersey). 'I'he exotherrn was noted and the mixture was then heated to 120 C2 for two hours. Table I is representative of' reactants and zwitterionic iminc corrosion inhibitors which were synthesized in this manner. I'rothcts 1-3 arc urlacrylated imines, synthesii,.cd for the purpose of'comparison to the acrylateci imincs of'tht instant invention, reprcsentcd by products 4- t 6.

Table I

_ Starting Materials Product Name Inhibitor TOFA/L)E'I'A' irnidazoline + propylidene TOFA/OETA irnidazoline propionaldehyde TOI A/DE'I'A' imiiazoline + furylidenc'l'OFAll)ETA imidazoline 2 ftrrfuralde}lyde TOFA/I-)E'l'A' imitiazoline propylidenc TOFA/DETA amitle l monoamine -a propionaldehydc Bengal oleylarnine acrylic acid 3-(benzylidene-Nolcyliminium) propionate 4

( cyclohexyli(lene oleyl amine -t acryl ic 3 -(cyelohexy I idene-N-oleyl iminillm) acid propionate n-propylidene oleylamine acrylic 3-(propylideneN-oleyl imillium) propionate G acid iso-propylidene oleylamirle + aclylic 3-(isopropyli(ltne-N-oleylimillium) 7 acid propionate furfurylidene oleylamine - acrylic 3-(furylitlene-N-oleyl iminium) propionatt acid benzal oleyldiamine + acrylic acid 3-(benzylidene-N-(oleylaminopropyl) iminiurn propiollate cyclohexyl idene oleyLliamine + 3 -(cyc lohexyl idene-N-(oleylaminopropyl) 10 acrylic acid iminium) propionate npropylidene oleyldiamille + acrylic 3-(propylidene-N-(oleyl aminopropyl) aeid iminiUITl) propionate iso-propylitlene oleyLli am ine acrylic 3(isopropylidene-N-(oleylaminopropyl) 12 acid iminium) propionate furfurylitlt ne oleyltliamille acrylic 3-(furylidene-N-(oleylaminopropyl) 13 acid iminium) propionate dodeeyl idene oleyldiamine + acrylic 3(dodeeylidene-N -(oleylaminopropyl) 14 aeid iminium) propionate dodeeylidene ethanolamine + acrylic 3-(dodecylidene-N-(hydroxyethyl) imillium) 15 aeid propionate propyliderle I (:)FA/DE I A' 3-(2(propylidelle TOFA/OETA' 16 imidazoline + acrylic acid imidazolinium)) propionate I = pro(luct of reactiol1 ol tall oil fatt:acitl and diethylene triamille in I: I mole ratio Example 2

Wheelbox coupon corrosion tests were conducted to evaluate the imille corrosion S inhibitors of the present invention synthesized as described in Example 1 in comparison

with conventional corrosion inhibitors. The tests were conducted at 80 C in a rotary oven. 'I'he coupons used were tlut and rectangular and made of carbon steel which had been water quenched and hardened. To prepare the coupons, metal surfaces were sand blasted, washed in an alcohol/toluerle mixture and ciried. Suitably prepared coupons were 5 weighed and placed individually in sample bottles.

The test medium was matte up comprising t)()% by volume of a seawater brine and 10% by volume of a paraffinic hydrocarbon. If}12S was used to simulate sulfide conditions, the paraffmic hydrocarbon used was sparged with ITS. Each bottle was dosed with a measured amount ot'tlle inhibitor to be tested ( 10, 25 or 50 ppm). Finally, I O the coupons were placed in the bottles which were then capped and shaken.

The oven was heated to 8() C and loaded with the coupon containing bottles. The bottles were rotated in the oven for a period of 24 hours. After cleaning and drying, the coupons were reweighed anti a percent corrosion inhibition was calculated using the formula: (average blank weight loss-weigllt loss of' treated coupon/average blank 15 weight loss x 100). Each coupon was also visually inspected and the appearance was recorded. In one set of corrosion tests, the htttle headspace was air. In another set of corrosion tests, additional steps were taken to exclude most of the air. Where a substantially air-free environment was desired, argon was bubbled through both the brine 20 and the hydrocarbon. Each of the inhibitors of'l'able I did show corrosion inhibition characteristics. Example 3

A "stirred kettle" apparatus was utilized to measure the corrosion inhibition 25 capabilities of the zwitterionic imines under several different fluid flow rates.

The stirred kettle apparatus used consisted of a one liter resin kettle with a flour neck removable top. An overhead stirred was used to agitate the fluids and a sparge tube was used to purge the fluids with N2 to remove any 02. A thermocouple and temperature controller were used to monitor/maintain the temperature of the system. The fluids used 30 for the tests consisted of varying ratios of brine and a mineral oil or kerosene. A baseline

corrosion rate was measltrcd and the system was then dosed with the corrosion inhibitor Corrosion rates were measured using a probe with two cicctrodes (reference and working;). 'I'he probes were conocctetl to a ('(-)RRA'I'I2R (Rohrbach Instruments Santa I.'c Springs Calif'onia) wilicl recorded corrosion rates at periodic intervals 'I'hc 5 CORRA'I'LSK usetl the method of linear polarization resistance (1.1'}) to detennine corrosion rates 'I'hc data was then do\vnloaded to a spreadsheet software prognan, which allowed graphical interpretation of' the results C'oncentration/dosage for each potential inhibitor tested was the same 'I'ahle 11 illustrates the results which provide a quantitative measure of corrosion inhibition Unacrylatecl imines 1-3 do not perform well I () at all in this test leach test was perfonned twice so two data points are listed for each reading Use of the zwitterionic imines 4 7 and 16 results in lower corrosion rate and greater protection than the unacrylated conventional treatment Table 11

_ Corrosion Corrosion (corrosion Rate Ratc after Ratc af'tcr Inhibitor before 2 hours % protcctir-'n 14 hours % protection Conventional 395/424 302/349 23/lX 76/101 X1/76 Formulation A' 4 5 1 6/249 1 36/80 7416X 5'3138 89/X4

7 4Y.'3/430 133/104 73176 61/46 o8/X9 1 6 532/545 I X2/ 1 XX 66. /65 47/45 9 1 /92

_.. I = unacrylated conventional inhibitor formulation containing quatcrnary amine and imidazoline active ingredients available from Nalco/Exxon F.nergy Chemicals 'L P of Sugar Land Texas

/ The present invention is illustrated by \vay of the foregoing description and

examples. 'I'he foregoing description is intended as a non-limiting illustration, since

many variations will become apparent to those skilled in the art in view thereof. It is intended tint all such variations within the scope and spirit ot'thc appended claims be 5 embraced thereby.

('twinges can he made in the conposition, operation and arrangement of'the mcttod ot'ttle present invention described herein \vithout departing t'rom the concept and scope of the invention as kenned in the following claims ].8

i CLAIMS

1. A zwitterionic water-soluble imine which is 3-(2-

(propylidene TOFA/DETA imidazolinium)) propionate.

s 2. A composition comprising: a) the zwitterionic water-soluble imine according to claim 1; b) a water-soluble surfactant; and 10 c) water.

3. The composition of claim 2 wherein the surfactant is ethoxylated alkyl amine or ethoxylated nonylphenol.

Is 4. The composition of claim 2 or claim 3, further comprising a pourpoint depressant which is an alcohol or glycol. 5. The composition according to any one of claims 2 to 20 4, further

comprising a co-inhibitor which is an amide, quaternized amine or amide amine salt.

6. The composition according to any one of claims 2 to 5, further comprising a filming agent which is p 2s toluenesulfonic acid or dodecylbenzenesulfonic acid.

7. A method of inhibiting corrosion in metallic flow lines for carrying fluids comprising adding to the

( fluids an effective amount of a zwitterionic water-

soluble imine according to claim 1 or of a composition according to any one of claims 2 to 6.

5 8. The method of claim 7 wherein the zwlLterionic imine is added to the flow lines continuously to maintain a corresponding inhibiting dose of from about 0.1 to about 500 parts per million.

lo 9. The method of claim wherein the zwitterionic imine is added to said flow lines continuously to maintain a corresponding inhibiting dose of from 1 to 250 parts per million.

15 10. The method of any one of claims 7 to 9 wherein said flow lines are made of mild steel.

11. The method of any one of claims 7 to 10 wherein the flow rate of the fluids through the flow lines is up to about 65 feet per second.

12. The method of claim 11 wherein the flow rate of the fluids throuc3h the flow lines is up to about 40 feet per second. 25 13. The method of claim 12 wherein the flow rate of the fluids through the flow lines is up to about 35 feet per second.

Claims (1)

1. Amendment to the claims have been filed as follows CLAIMS

   1. A zwitterionie water-soluble imine which is,-(-(propylitlene TOF.A/I) E:TA imidazolinium)) propionate.

   9. A conlpositic.n comprising: a) the zNvitterionic \iater-soluble incline aeeortlinc, to claim 1; h) a water-soluble stirfactant; and c) mater.

   it. Tlle composition of'claim wllcrcin the surlactant is cthoxylated alkyl amine or ethoxylated nonylpllenol.

   4. I he composition of claim or claim 3, further comprisin<, a pour-point 15 dtpressant ']liCh is an alcohol or Iycr.'l.

   5. I he coinp>sition aeeortling to any one of claims to 4, f;rtller comprising a .........

   eo-nhbkr W}ItCh IS an made guaterinz.ec! amine or anode amine salt.

   0() 6. I he coml:.siti.'n accortling to any one,f claims 2 to 5. further comprising a fIlminjg agent which is p-to}lenesullonic cacitl or d-> decylLcnzenesulfonic acid.

   7. A method.,i inhibiting corrosion in metallic flow lines for carte ing fluids co'nprisin;. aciding to the fluids an effective amount of a z. wittcrionic Natcr-soluble 05 Irvine accordin, to claim I or of a composition according to any one of claims 2 to 6.

   l 8. The method of claim 7 wherein the z.\N;itterionic iminc is adUcd to the flow lines continuous!! to maintain a corresponding inhibiting dose ol'f'ron1 I to about 50() parts per million.

   s 9. The method of claim S wherein the zwitterionic imine its acicicd to said flow lines continuously to maintain a corresponding' inhibiting Incise of'I'r<->m I to 250 parts per million.

   10 1(). 'l'he method of an>; one of'claims 7 to to wherein said flow 1incs are macic of mild steel.

   11. 'I'hc mctilod of ally one of clain.s 7 to 10 \N'}lCi-Cin the flow rate of'the fluids through the flow lines is Up to 65 feet per second.

   1?, 'I'he netilod of claim 1 1 wilercin the flow rate ct't}lC fluids through the flow lilies is up to 4() feet per second.

   13. 'I'he ncthod of claim 12 whcrcin the flow rate of'the fluids tlrougl1 the flow 20 lines is Up to 35 feet per scccncf.

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