CA1085154A - Corrosion inhibitor compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Improved corrosion inhibitor compositions especially for hydrocarbon fuels are described consisting of mixtures of from about 75 to 95 weight percent of a polymerized unsat-urated aliphatic monocarboxylic acid having about 16-18 car-bons with about 25 to 5 weight percent of a monoalkeylsuccinic acid wherein the alkenyl group has 8-18 carbons. Also des-cribed are concentrates of the above compositions in hydro-carbon solvents and fuels containing the compositions.

Description

~35154 BACKGROUMD OF THE INVENTION
1. ~leld of the Invention -~ hls invention relates to novel corroslon inhibi-tor composition~.

2 Prlor Art Storage tanks and pipelines for liquid hydrocarbon fuels are unavoidably exposed to corrosive environments, re-sulting primarily from water contamination of the systems. In addition to the substantial economic loss in maintenance and replacements of the storage and pipeline equipment, the in-corporation of the corrosion products into the hydrocarbon ~uels can also create fuel quality problems.
~ hile a variety of oll-soluble corroslon inhlbitors are known for hydrocarbon sy~tems~ those suitable for ~uels must meet certain important requirements not generally re-quired of, say, lubricating oil compositions. One requirement is that the corroslon inhibitor must be effective in very small amounts, not only to minimize co~ts but also to minimize certain other adverse effects such as the contribution to the existent gum specifications of the fuels. The second importan-t require-ment ls that the amounts used to effectlvely lnhibit corrosion should not impart undesirable emulsiflcation characteristics to the fuels.
U.S. Patent 2,671,979 discloses the use of polymerized linoleic acid, especially the dimer thereof, as rust inhibitors for oils, motor fuels, emulsions, polymers, pollshes, paints, and sprays. U.S. Patent 2,632,695 discloses the use of poly-merized C16_18 unsaturated monocarboxylic acids, especially the dimers thereof, as rust inh$bitors for mineral oil products such as gasoline, naphthas and burning oils ~t, - 2 - ,~
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~ 4 U.S. Patents 2,124,628 and 2,741,597 di~close the use of alkenyl~uccinic acids a~ antiru~t agents in mineral lubricating oil~.
U.S~ Patent ~,208,945 discloses a combination of a polymerized linoleic acid an* e monoalkenylsuccinic anhydr-ide having 8 to 18 carbon atoms in the alkenyl group as antirust ~gent in mineral lubricating oils.
A need still exists for a corroslon inhibitor for hydrocarbon fuels which is ef~ective in very low concentrations and which does not lmpart undesirable emulsi~ication character-16tics in the fuels.
SUMMARY OF THE INVENTION
~he pre~ent invention consi6ts of a corrosion inhi-bltor compo~ition con6istinK e~sentially of, by weight~
(a) from about 75 to 95% of at least one polymer-ized un~aturated aliphatic monocarboxylic acid (e.g., dimerizedor trimerized acid) having from about 16 to 18 carbon atoms per molecule, and (b) from about 25 to 5~ Of a monoalkenylsucclnic acid in which the alkenyl group has 8 to 18 carbon atom~.
Al60 included ln the invention are: a concentrate con6i6ting e6~entially o~, by weight, (a) from about ~5 to 85~ of a compo~ition of the definition above, and (b~ from about 65 to 15~ of a hydrocarbon ~olvent;
and a hydrocarbon fuel containing an effectlve corro6ion -inhibiting amount of a compo6ition of the definition above, 35~S;4 3ETAILS OF TIE I~ ~rrIO~J
Dimerized and trimerized acids prepared by the poly~
merization of polyunsaturated aliphatic monocarboxylic acids are ~Jell kno~m in the art. ~escriptions of the preparation and pxoperties of dimer and trlmer acids can be ~ound for example in the Journal of the American Oil Chemists' Socie~y 24, 65-68 (19~7) and in U.S. Patents 2~82J761; 2,631,979;
2,632,695; and 2,794,782. As sho~ in the art, dimer acids can be prepared by heating under pressure ~n unsaturated fatty acid in the presence o~ a small amount of ~ater at a tempera-ture of 260-360~C for 3-8 hours. me dimer acid thus produced usually also contains some unpolymerized ~onocarboxylic acid, some trimer acid and some higher polymeriæed acids. I~
desired, the amount of the trimer acids can be increased b~
r~ry~ng the reaction condltionsO
Whlle either dimer or trimer acids can be used ln the practice of the present inventlon, ~or practical reasons, commercially available dimer and trimer acids which contain varying proportions o~ dimer and trimer acids as well as mono-carboxylic acids are normally used. For example, commerciallyavailable dimer acid (e.g., "Empol"* Dimer Acids, Emery Industries), prepared by polymerizing linoleic acids, contain ~rom l~o to 95% dimer acids ~nd ~rom )~ to 25~ trlmer acids. Com-mercial trimer acids (e.g., "Empol" ~rimer Acids), contain ~rom 40 to 95~ trimer acids and ~rom 5 to 25~ dimer acids. Both types o~ compositions m~y contain up to 25~ o~ monocarbo~ylic acids. ~-Because of their availability and 10~J cost, mix~ures o~ fatty acids containing predominantly unsaturated aliphatic monocarboxylic acids o~ 16 to 18 carbon atoms~ such as tall oil fatty acids, are o~ten used to produce dimer and trimer * denotes trade mark ~8~5~

acld compositions. Polymerized tall oil fatty acids, such as "Acintol"~ FA-7002 (Arizona Chemical Company) are also satisfactory in the lnvention compositions. A typical analysis of "Acintol" FA~7002 (in weight percentages) is as rOllOws:
Acid Value 143 Rosin Acid, ~ 13 Unsaponifiables % 3 Monomers ~ 18 Dimers, % 66 High Polymers, % 16 Accordingly, the polymerlæed unsaturated monocarbox-yllc acid~ are tho~e which are pr~pared ~rom un~aturated mono-cRrbox~lic acld~ o~ 16 to 18 carbon atoms, con~ain at least about 75% dimerlc, trimeric and higher polyrnerized acids, wlth the dimeric acids preferably representing at least about 50 o~ such polymerlc acids, and contain not more ~han about 25%
monocarboxylic acids. For convenience, the above-described polymerized unsaturated monocarboxylic acid composi~ion will be referred to as dimer acid, it being understood that said de~i~nation encompasses acid compositlons whlch may con~ain monocarboxyl~c, trimeric, and higher polymerlc acids ln addition to the dimeric acids. I
Monoalkenylsuccinic acids are also well known ~n the art. These acids are readily prepared by ~he condensation o~
an olefin with maleic anhydride followed by hydrolysis (e.g., UoS~ Patents 2,133,734; 2,7~1,597). Suitable ~onoalkenyl-succinic acids include oc~enylsuccinic acid, decenglsuccinic acid, t~decenylsuccinlc ~cid, dodecenylsuccinic acid, penta-decenylsuccinic ac~d, octadecenylsuccinic acid and i~omers ~ denotes trade m~rk thereof having alkenyl groups of varlous hydrocarbon struc-tures. The preferred monoalkenylsuccinic acid ls dodecenyl-succlnic acld, more preferably dodecenylsuccinic acld prepared by utilizing propylenetetramer.
-The present invention is based on tlle di~covery that comblnations of a dimer acid with a monoalken~ylsuccinic acid as defined, ln proportions by weight, of from 75 to 95~ dimer acid and 5 to 25~ monoalkenylsuccinic acid, provide outstand-lng corrosion inhibition in hydrocarbon fuels at very low concentrations. In fuel compositions such co~binations of dimer acids and monoalkenylsuccinic acids inhibit rusting to a degree which would not be expected from the performance of the components alone in the same ~uel. The pre~erred c:ombi-nation will contain, by weight, Prom about 80~90~o dimer acid and frorn about 10 to 20~ monoalkenylsuccinic acid. The more preferred combination will contain from about 84 to 86~ dimer acid and from about 14 to 16~ monoalkenylsuccinic acid. The above-indicated weight ratios, particularly in the preferred combinations, are based on the practical consideration of high effectiveness, low cost and good water-interactlon properties.
Since the monoalkenylsuccinic acids are costlier than the dlmer acids, it i8 therefore desir~ble to utilize the more costly monoalkenylsuccinic acid in minimum amounts in the com-bination consistent with effective corrosion inhibiting prop-erties.
The hydrocarbon fuels into which the present inven-tion compositions are incorporated to provide corrosion in~
hibiting characteristics are normally liquid hydrocarbon fuels boiling in the range of about 70F to about 700F and include motor gasolines, aviation gasolines, Jet fuels, kerosenes, die~el ~uels, and fuel oil8. The hydrocarbon fuel composi-tions containing the lnvention compositions as corrosion in-hibitors may also contain conventional additives used ln hydro-carbon fuels such as antiknock compounds, antioxidants, metal deactivatorsj other corrosion inhibitors~ antistatic agents, antiicing agents, detergents, dispersants, thermal stabilizers, dyes and the like.
The composition of the invention incorporated into hydrocarbon fuels in the range of about 0.0002 to 0.002 per-cent by weight (0.5 to 5 pounds per thousand barrels, ptb)provide satisfactory corrosion-inhibiting properties. Concen-trations higher than 0.002~ may be used but do not appear to provide further benefits. The preferred concentration range 1~ ~rom about 0.003 to 0.0016 percent by welght (0.075 to l~ ptb), the more perferred range i8 ~rom about 0.0004 tO 0.0012 per-cent by weight (1 to 3 ptb).
The corrosion-inhibitor compositions of the inven-tion can be added to the hydrocarbon fuels by any means known in the art for incorporating sma11 quantities of additives into hydrocarbon fuels. The dimer acid and the monoalkenyl-~ucclnic acld may be added separately or they may be combined ~nd added together. It is convenient to utilize the present compositions as concentrates, that is, as concentrated solu-tions in suitable solvents. When used as a concentrate, the additive composition will contain from about 35 to 85% by weight of the dimer acid-alkenylsuccinic acid combination and from about 65 to 15~ by weight of a solvent. The preferred concentrate will have from about 60 to 80% by weight of the combination and from about 20 to 40~ by weight solvent, the more preferred concentrate will have ~rom about 72 to 77% by weight of the dimer acid-monoalkenylsuccinic ~cid combination a~d from about 23 to 28~ solventO Suit~ble solvents are ~ 5~5~

normally liquid organic compound~ bolllng in the hydrocarbon ~uel bolling range, particularly hydrocarbon~ ~nd alcohol6, an~ lnclude hexane, cyclohexane, heptane, octane, iaooctane, benzene, toluene, xylene, methanol~ e-thanol, propanol, buta-nol, gasolines, ~et fuels, ~uel oils and the llke. Mixtures of ~olvents can also be used. The preferred solvent is xylene.
U.S. Patent 2,632,695 (Iandis et al.) cited above teaches that the requirements and performances of corrosion lnhibitors depend upon whether the hydrocarbon substrate is a lubricatlng oil or a nonlubricating hydrocarbon fractlon, such as fuels. Thus the patentees show (at column 14, :Line 41 - column 15, line 32) that whlle dimer acids are effective corro~ion l~nhibitor~ a~ 0.001 weight percent in hydrocarbon ruels, the same dimer aclds at 5 weight percent are inef~ec-tive in turbine oils.
As mentioned, dimer acids are known in the art as effective corrosion inhibitors in hydrocarbon fuels. Alkenyl-~uccinic acids on the other hand while known as corrosion inhibitors in lubricating oils, are not generally recognized as e~ficient corrosion inhibitors in hydrocarbon fuel~. It is thcrefore unexpected that the combinations of di!ner acids and monoalkenylsuccinic acids provide corrosion inhlbition greater than that anticipated from the results obtained with the indi-vidual components of the combinations. Even more unexpected is the discovery that the combinations of dimer acids and monoalkenylsuccinic acids are considerably better corrosion inhibitors than the combinations of dimer acids ~nd monofllkenyl-succinic anhydrides.
EXAMPLES 1~4 Antirust per~ormances o~ the invention compositions were determined accordlng to NACE (Nation~l Associatlon o~
Corroslon Engineers) Standard TM-01-72 "Antlrust Propertles of :10~51 54 Petroleum Products Pipellne Cargoes." The test method is essentially ~STM D665 method ~odified to determine antlrust properties of gasolines and distillate fuels in movement through product pipelines. The method involves stirring a mixture of the test fuel and distilled water for 4 hours at 38C with a cylindrical steel specimen immersed in the mixture. The anti-rut rating is based on the portion of the test specimen ex-posed within the test fluid and is expressed using the follow-ing rating scale:
Rating~ Proportion of Test Surface Rusted A None B~+ Less than o.1~ ~2 or 3 spots of no more than 1 mm iame-ter) ~ ~ Less than 5 B 5 to 25 C 25 to 50 D 50 tO 75%
E 75 to 100~
Ordinarily a rating o~ B~ or B~ is adequate to con-trol corrosion in active pipeline, although a rating of A is obviously more desirable.
The dimer acid ("Acintol" FA-7002~ Arizona Chemical Co.) was combined with dodecenylsuccinic acid in the weight ratios indicated in the Examples below and dissolved in xylene to provide concentrates containing 79~ by weight o~ the combi-nation. The concentrates were added to depolarized isooctane in the concentrations indicated. The tests were run in dupli-cate. For comparison purposes, similar concentrates were prepared using dodecenylsuccinlc anhydride instead of the dodecenylsuccinic acid and similarly tested. The results are ~o summariæed below.

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The above examples show that the dimer acid-dodecenyl-succinlc acid combinations provide effective rust protection at very low concentrations. The above results also show that the dimer acid-dodecenylsuccinic acid combinations having the preferred ratios are markedly superior to similar combinations involving dodecenylsuccinic anhydride. Thus at 81/19 ratio (Example 2 and Compsrison Example 2), twice as much of the dimer acid-dodecenylsuccinic anhydride combination is required as the dimer acid-dodecenylsuccinic acid combination to obtain rust-free specimen (A rating). Similarly at 86/14 and 91/9 ratios (Examples 3 and 4, Comparison Examples 3 and 4) , the combinations containing the dodecenylsyccinic acid are greatly superior to the combinations containing the anhydrlde, The above re~ult5 also show that the dimer ~cid-dodecenylsuccinic acid combinations inhibit rustlng to a con-siderably greater extent than would be expected considering the expected contribution of each component of the combination.
Based on the concentrations of the dimer acid (Comparison Example 5) and of the dodecenylsuccinic acid ~Comparison Example 6) needed to provide a rust-free specimen (A rating), the ~uel concentration of any particular mixture of the t~ro which would be expected to provide rust--free specimens can be readily determined (e,g.,graphically). The following table compares the fuel concentrations of the combinations expected to provide rust-free specimens to the concentration~ actually found necessary to provide such protection in the NA~ test, 108~54 ~ABLE II
CONCENTRATION FOR N _ E 1'EST A RATING

Concentratlo ~ (lb./IOOO bbl) , for Rust-free Specimen Example Ratl ~ Expected F?und 1 7fi/24 2.5 0~75 2 81/19 2.6 1,0 ~ 85/14 2.7 1.0 4 91/9 2.8 1.5 , 79 weight ~ solution of dimer acid~dodecenylsuccinic acid in xylene Dimer Acid ~ a~io~ -;~ ' Dodecenylsuccinic Acid From the above, it can be seen that the inventlon c~mpositions are slgnificantly more efficient corrosion inhibitors than expected.

A representative corrosion inhibitor of the present invention was compared in efficiency ~ith varlous commercial corroslon inhibitors quallfied under MIL-1-25017-10 specifica-tions, Qualified corroslon lnhlbitors are those acceptable to the military ~or use in automotive gasolines, aviation gasolines and turbine fuels, The corrosion tests were carried out by the NACE Standard TM-01-72 procedure as decribed in the previous examples.
The combination of Example ~ was used as a 79~ solution in xylene. The commercial corrosion inhibitors were used as purchased. The results are summarized below, .
.

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~ ~ X ~ o ~ ~ , ~ 5 The re~ults of Table III show that the pres~nt in-vention composition, in being useable at lower concentrationc9 provldes a higher degree of rust protectlon ef~iciency than any of the commercial corrosion inhibltor~ tested.

Water Separation Index, Modified (~JSIM), ~hich is a nu~erical rating indicating the ease of separating water ~rom fuel by coalescence ~as determined by ASTM D 2550 Method, "Water Separation Characteristics of Aviation Turbine Fuels,"
~0 carried out by minisonic (MSS) mo~ification. The method in-volves preparation of a water-fuel emulsion3 metering the emulsion through a gla8~ fib~r coalesc¢r, and photometrlcally measurin~ the turbidlty due to entralned water. The WSIM
rating ~g from O to 100 wlth the hi~her number indlcating greater ease of water ~eparation. Ordinarily, an acceptable additive for turbine ~uel~ should have a WSIM rating of not le~s than 70 in use concentrations. WSI~ ratings of inven-tion compositions are summarized below.
TABLE IV
20~lATE~ .SEP~RATIO~ INDEX, ilODIFIED
Method: ASTl,l D 2550 Fuel: JP-4 Jet fuel Concentration ~JSII~l -Additive Wt Rati~~ Lb /lOOO bbl. ~It. ~ Rating None ~ _ _ 94 Example l 76/24 0.75- 0.0003 90 Example l 76/24 l.O 0.0004 88 Example 2 81/l9 l.O 0.000l~ 94 Dimer Acid ~ t- Ratio Dodecenylsuccinic Acid ~(~8~L5 The above results show that the present invention comp.ositions do not interfere with the separation of water from fuel at the stated concentrations~ which concentrations include those at whlch the invention compositions show excellent antirust activity (Table I). ~ .

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Claims (10)

I CLAIM:

1. A corrosion inhibitor composition consisting essentially of, by weight, (a) from about 75 to 95% of at least one poly-merized unsaturated aliphatic monocarboxylic acid, said unsaturated acid having from 16 to 18 carbons per molecule, and (b) from about 25 to 5% of at least one mono-alkenylsuccinic acid in which the alkenyl group has 8 to 18 carbons.

2. The composition of claim 1 in which the poly-merized unsaturated aliphatic monocarboxylic acid is poly-merized tall oil fatty acid.

3. The composition of claim 1 in which the poly-merized unsaturated aliphatic monocarboxylic acid is linoleic acid.

4. The composition of claim 1 in which the mono-alkenylsuccinic acid is dodecenylsuccinic acid.

5. A corrosion inhibitor composition of claim 1 consisting essentially of (a) a polymerized tall oil fatty acid, and (b) dodecenylsuccinic acid.

6. A corrosion inhibitor concentrate comprising about 35 to 85% by weight of a composition of claim 1 in at least one normally liquid member of the group con-sisting of hydrocarbons and alcohols.

7. A concentrate of claim 6 containing a poly-merized tall oil fatty acid.

8. A concentrate of claim 6 containing a poly merized linoleic acid.

9. A concentrate of claim 6 containing dodecenyl-succinic acid.

10. A concentrate of claim 6 containing a poly-merized tall oil fatty acid and dodecenylsuccinic acid in xylene.