CA1214631A - Liquid fuels containing corrosion inhibitors, and inhibitor concentrates - Google Patents

Abstract

ABSTRACT

LIQUID FUELS CONTAINING CORROSION
INHIBITORS, AND INHIBITOR CONCENTRATES

Corrosion caused by gasohol or alcohol motor fuels is inhibited by the addition of a corrosion inhibiting amount of the combination of (A) a polymer of one or more C16 to C18 polyunsaturated aliphatic monocarboxylic acid (e.g. linoleic dimer and/or trimer) and (B) a hindered phenol antioxidant, e.g. 2,6-di-(?-methylbenzyl) -4-nonyl phenol.

Description

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, ~:., ;, LIQUI~ FUELS CONTAINING CORROSION
INHIBITORS, AND INHIBITOR CONCENTRATES

In the past metal corrosion caused by conventional -~i motor fuels such as gasoline was not much of a problem ~j~ because such hydrocarbon fuels are inherently non-....
corrosive. Howeverr with the advent of fuels containing alcohols such as gasohol o~ straight alcohol fuels, corrosion has become a major problem because such fuels , j;~,~
are corrosive. It has been reported that this corrosion is due to the presence of acidic contaminants in such , ;~;
fuels such as formic acid. It is almost impossible to avoid such contaminants because they occur in fuel grade alcohols and are also formed in storage as normal alcohol `L~ oxidation products.
~ It is known from U.S. 4,305,730 that polymerized - ~,, :~ linoleic acid, especially trimer, is an effective corrosion inhibitor for alcohol-type motor fuels. It has now been discovered that the corrosion inhibiting properties of such polymerized polyunsaturated aliphatic ~ monocarboxylic acids are improved by use of the co-`~ additives described herein : - ' c lZ1463~
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According to the present invention metal corrosion caused by alcohol-type motor fuels is inhibited by adding to the fuel a combination of (A) polymerized polyunsaturated aliphatic monocarboxylic acid and (B) ,I;b 5 a sterically hindered phenol.
., i The invention provides a liquid fuel adapted for ',;
:, use in an internal combustion engine said fuel comprising from 5 to 100 weight percent of one or more alcohols, from 0 to 95 weight percent gasoline and a corrosion ` 10 inhibiting amount of the combination of (A) a polymer . .
- of one or more C16 to C18 polyunsaturated aliphatic i`
- monocarboxylic acids and (B) at least one sterically ;~: hindered phenol.

~! The additive combination of this invention can ; 15 be beneficial in any engine fuel containing or consisting of an oxygenate. Such fuels include gasoline-alcohol mixtures referred to as "gasohol" as well as straight alcohol fuels. Useful alcohols are methanol, ethanol, :: .
n-propanol, isopropanol,isobutanol and the like.
20 Gasohols usually contain about 2 to 30 volume percent - alcohol. The most prevalent alcohols are methanol and ethanol. At concentrations above 10 volume percent phase separation problems are encountered especially in the presence of water.

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-~ - 3 -~ Phase separation can be minimised by including co-`:
~, solvents in the gasohol such as ethers, ketones, esters ~, and the like. An especially useful co-solvent is methyl tert-butyl ether which also serves to increase octane ..
,s 5 value.
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- The additive combination may be used at a ; - i .~ concentration which provides the required amount of ~ corrosion protection. A useful range is about 1 to , .
5000 parts per million (ppm). A more preferred range is about 5 to 2000 ppm and the most preferred concentration is 10 to 500 ppm.
" , , Component A is a polymer of one or more 16 to 18 carbon polyunsaturated aliphatic monocarboxylic acids. Examples of these are linolenic acid and linolenic ~-s 15 acid including mixtures thereof. The polymers comprise mainly dimers and trimers of the polyunsaturated acids.
Suitable polymers of linoleic acid are available commercially. Mixtures high in trimer content are most ; preferred.
~ 20 Component B of the combination is a hindered :,~
phenol. This includes any fuel (i.e. gasohol or .
alcohol fuels) soluble phenol having at least one bulky substituent ortho to a phenolic hydroxyl group.

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;-~ Representative bulky substituents are secondary and tertiary alkyl (including cycloalkyl and alkyl (cycloalkyl) or aralkyl groups.
More preferably the hindered phenols are sub-~ 5 stituted in both positions ortho to a phenolic hydroxyl -~ group with a secondary or tertiary alkyl or aralkyl group. Such phenols include

2,6-di-sec-butylphenol 2,6-diisopropyl phenol -~ 10 2,6-di-tert-butylphenol ~' 2,6-di-sec-octylphenol 2-tert-butyl-6-(4C-methylbenzyl)phenol 2-isopropyl-6-(C~, d -dimethylbenzyl)phenol 2,6-di-(C~-methylbenzyl)phenol 2,6-di-(C~,C~ -dimethylbenzyl)phenol and the like.
In a highly preferred embodiment the hindered phenols are also substituted in the para position with an alkyl group containing 1 to about 20 carbon atoms.
~,; Examples of these hindered phenols are ;,~.
2,6-di-tert-butyl-4-methyl phenol 2,6-di-tert-butyl-4-ethyl phenol - 2,6-di-tert-butyl-4-(n-butyl) phenol 2,4,6-tri-tert-butyl phenol '' ~.~

, -r''i `~3 2,6-di-tert-butyl-4-(sec-octyl) phenol 2,6-di-tert-butyl-4-(sec-eisosyl) phenol 2,6-diisopropyl-4-methylphenol 2,4,6-tri-sec-butyl phenol and the like.
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In a still more preferred embodiment the hindered phenol 1S a 2,6-d~-(0~-methylbenzyl)-4-Cl-20 alkyl phenol. These include 2,6-di-(C~-methylbenzyl)-4-methyl phenol 2,6-di-(OC-methylbenzyl)-4-ethyl phenol 2,6-di-(C~-methylbenzyl)-4-tert-butyl phenol 2,6-di-(CY-methylbenzyl)-4-(n-butyl) phenol .,; ~i, 2,6-di-(C~-methylbenzyl)-4-(sec-octyl) phenol ~ 2,6-di-(CC-methylbenzyl)-4-nonylphenol -~ 2,6-di-(oC-methylbenzyl)-4-dodecylphenol ~ i 15 2,6-di-(CC-methylbenzyl)-4-octadecylphenol ~, , 2,6-di-(CC-methylbenzyl)-4-eicosylphenol and the like.
` ; Sterically hindered methylenebis phenols are also '.x~
-~ useful. These include 2,2' methylenebis-(4-alkyl-6-tert-alkyl phenols)and 4,4' methylenebis (2-alkyl-6-tert-alkyl phenols).

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`~i Representative examples of these are 2,2-methylenebis P (4-methyl-6-tert-butyl phenol), 2,2' methylenebis--- ~4,6-di~tert-butyl phenol), 4,4' methylenebis (2,6-di-tert-butyl phenol), 4,4'-methylenebis-(2-methyl-~ 5 6-tert-butyl phenol) and the like including mixtures -s~ thereof.
The most preferred hindered phenol is 2,6-di-( ~ -methylbenzyl)-4-nonylphenol. The nonyl group is readily available by alkylation with propylene trimer.
The weight ratio of component A to component B
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in the combination can vary over a wide range such as 1 to 10 parts A to 1 to 10 parts B. In a more preferred embodiment the weight ratio is about 0.5-5 parts component A for each part component B. In a still more preferred embodiment there are 0.6-4.0 parts component A
--~' per each part component B. The most preferred ratio i S 1 1 .
Components A and B can be separately added to the , fuel. More preferably components A and B are pre-:
mixed to form a package and this package is added to the fuel in an amount sufficient to provide the required ~-- degree of corrosion protection.

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Most preferably components A and B are also pre-mixed with a solvent to make handling and blending ,,;~
easier. Suitable solvents include alcohols (e.g.
;~ methanol, ethanol, isopropanol) ketones (acetone, --~
~ 5 methyl ethyl ketone)esters (tert-butyl acetate) and ~ .
~ ethers (e.g. methyl tert-butyl ether).
;~ Aromatic hydrocarbons are very useful solvents.
- These include benzene, toluene, xylene and the like.
Excellent results have been obtained using xylene.
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- 10 The concentration of the active components A and B in the package can vary widely. For example the . ~.
active content can range from about 5 weight percent up to the solubility limit of A or B in the solvent.
With xylene a total active content of about 5-25 weight , ..~.
~ 15 percent is generally used, especially about 10 weight ;~ percent.
;,~ Tests were conducted to measure the anti-corrosion - ~ t properties of the additive combination. In the test the corrosion of metal coupons immersed in test fluid -~ 20 was measured under different test conditions. Aluminium, brass, zinc, lead and copper coupons were used. The coupons were first cleaned with carborundum 40, washed with petroleum ether and oven dried for 10 minutes at 40C.
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-~- Each coupon was weighed and then immersed in 130g of the test fluid in a sealed bottle for the specified time at `` the specified temperature.
At the end of the test period, the coupons were removed from the fuel; after loose deposits were removed with a light brush, the coupons were washed and dried . . ~
as at the start of the test and then reweighed. Any change in coupon weight was recorded. Both gain and ... ,~: .
loss of weight indicate corrosion.
--, 10 The corrosion was characterised by two modes, either ~ weight loss by loss of metal or weight gain due to .~ deposition of corrosion products, in the tests carried out below, visual examination of the coupons after test indicated that the two modes were mutually exclusive.

; 15 The first series of tests was conducted in various alcohol type fuels containing 100 ppm of the equal weight combination of linoleic acid polymer (mainly trimer) and 2,6-di-(C~-methylbenzyl)-4-nonylphenol.

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In this test series the temperature was ambient and immersion time 6 weeks. Results are given in the following table in terms of mg weight gain or loss. The value in parenthesis is the result without any inhibitor.

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Test Fuel Metal Gasoholl Wet Gasohol Wet Methanol3 Aluminium 0.O (+0.3) +0 5 (+0.5) 0 (-o.8) 10 Brass +0.4 (-0.5) -0.3 (~ 9) -0.1 (-1.0) ;' .!
Zinc +0.1 (-0.2) +0.1 (+0.2) +0.1 (-1.1) ~'~ Lead +0.9 (+0.1) -0.4 (-0.1) -224 (-408) Copper -0.3 (-o.8) -0.3 (+0.4) +0.4 (-1.6) ';'~.:
:,, 1 : 15 Contained 15 vol percent methanol Same plus 0.1 weight percent water ;. 3 ` Contained 0.1 weight percent water . .

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In the next test series the coupons were placed in a bottle containing methanol doped with 100 ppm formic acid and 10 ppm methyl formate to increase test severity.
The test additives were equal weight mixture of linoleic acid trimer and various hindered phenols as shown in Table II. Additive concentration was 100 ppm. The - bottles with the test coupons were stored two weeks at ~ 40C. Weight change due to corrosion is shown in -~ Table II.
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TABLE II

,, Weiqht Chanqe (mq) Hindered Phenol Brass Lead Aluminium Blank + 0.3 - 347 - 1.8 l - 1.7 - 304 - 0.2 r 15 z2 _ 0.1 - 294 0 , .. .
ly is a mixture of tert-butyl phenols comprising mainly 2,6-di-tert butylphenol.
:~`.`! 2 ;~ Z is 2,6-di-k~-methylbenzyl)-4-nonylphenol i ,l Further tests were conducted which show the syner-gistic results obtained with this combination of additives.
These tests were in methanol doped with 100 ppm formic acid and 10 ppm methyl formate. The metal coupons were immersed in the fuel and stored two weeks at 40C.

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Additive D was 2,6-di-(CC-methylbenzyl)-4-nonyl-phenol. Additive E was linoleic acid trimer. Additive D + E was an equal weight mixture of D and E. Total inhibitor concentration in each test was 300 ppm.
TABLE III
Additive , . ..
Metal D E D + E

Copper -0.7 +0.3 -0.9 Lead -525 -454 -340 `z 10 Brass +0.2 -6.8 +0.6 ; Aluminium -0.5 -1.1 +0.6 -~ Zinc -4.2 -7.8 -1.0 .. , ; .
~. ` These results show that the combination gives , . ~ .
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~ better results than would be expected from the results ,..,~
- 15 obtained with each component.

In the next test series the fuel was methanol doped with 100 ppm formic acid and 10 ppm methyl formate. The ~ metal coupons were only partially immersed (approx 50%) -~ and the bottles were stored two weeks at 40C. The -~
additive was a 50/50 mixture of linoleic acid trimer and 2,6-di-(oC-methylbenzyl) phenol. Additive con-centration was 300 ppm in each samples. Test results are given in Table IV.

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,, Weiqht Change (mq) - Metal Blank Inhibited `~' 51 c Copper + 4.1 - 0.2 ~ ~ 5 Lead - 351 - 263 ,~,, ~ Brass + 1.7 + 1.2 ,.:2 ~, Aluminium + 2.9 - 0.2 .~
Zinc - 3.3 - 0.8 The next test was again conducted in gasohol -, ~
~ containing 15 vol percent methanol and doped with 100 ppm --~ 10 formic acid and 10 ppm methyl formate. The metal coupons ,' were fully immersed and stored two weeks at 40C.
~' Additive concentration was 100 ppm. Table V gives the ,,.,~A test results with and without the test additive. The test additive was an equal weight mixture of linoleic ` 15 acid trimer and various hindered phenols as indicated.
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TABLE V
Coupon Weight Change Additive Lead Aluminium Copper - None -146 mg +0.9 mg -8.0 mg ` 20 Ml -119 +0.5 -4.2 -~ N -104 +0.3 -6.2 0 -112 +0.2 -5.8 M is linoleic acid trimer plus 2,6-di-(C~-methylbenzyl) phenol 25 N2 is linoleic acid trimer plus mixture of :

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methylene-bridged 2,6-di-tert-butyl phenol ~'~ and ortho-tert-butyl phenols.
03 is linoleic acid trimer plus 2,6-di-tert-butyl-4-_-butyl phenol.
The test results show that while not equally effective on all metals in all fuels, the additive combination on average gives very good corrosion protection.
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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A liquid fuel adapted for use in an internal combustion engine, said fuel comprising 5 to 100 weight percent of one or more alcohols, 0 to 95 weight percent gasoline and a corrosion inhibiting amount of a com-bination of (A) a polymer of one or more C16 to C18 polyunsaturated aliphatic monocarboxylic acids and (B) at least one sterically hindered phenol.

2. A liquid fuel as claimed in claim 1 wherein said polymer of one or more C16 to C18 polyunsaturated aliphatic monocarboxylic acids comprises mainly linoleic acid dimer, trimer or mixtures thereof.

3. A liquid fuel as claimed in claim 1 wherein the or each said hindered phenol is substituted in both positions ortho to the phenolic hydroxyl group with a secondary or tertiary alkyl or aralkyl group.

4. A liquid fuel as claimed in claim 3 wherein said phenol is a 2,6-di-(?-methylbenzyl)-4-C1-20-alkyl-phenol.

5. A liquid fuel as claimed in claim 4 wherein said phenol is 2,6-di-(?-methylbenzyl)-4-nonylphenol.

6. A liquid fuel as claimed in claim 3 wherein said phenol is a 2,6-di-tert-butyl-4-C1-20 alkyl phenol.

7. A liquid fuel as claimed in claim 6 wherein said phenol is 2,6-di-tert-butyl-4-butylphenol.

8. A liquid fuel as claimed in claim 6 wherein said phenol is 2,6-di-tert-butyl-4-methylphenol.

9. A liquid fuel as claimed in claim 3 wherein said phenol is 4,4'-methylenebis-2,6-di-tert-butylphenol).

10. A corrosion inhibitor concentrate comprising a solvent containing at least 5% by weight of a combination of (A) a polymer of one or more C16 to C18 polyunsaturated aliphatic monocarboxylic acids and (B) at least one sterically hindered phenol.