CA2118618C - Distillate fuel composition containing combination of copper corrosion inhibitors - Google Patents

Abstract

A distillate fuel composition for reducing copper corrosion in fuel delivery systems and internal combustion engines which comprises a synergistic combination of (a) a 2,5-dihydrocarbyldithio-1,3,4-thiadiazole of the formula

Description

BACKGROUND OF THE IN~IENTION
1. Field OfThe Invention This invention relates to a distillate fuel composition containing a thiadiazole and a tolyltriazole adduct as copper corro-sion inhibitors, and its use to reduce copper corrosion in fuel delivery systems and internal combustion engines.

2. Description Of The Related Art It is well known that elemental sulfur, hydrogen sulfide and other sulfur compounds, contained in hydrocarbon streams are corrosive and damaging to metal equipment, particularly copper and copper alloys. Sulfur and sulfur compounds may be present in varying concen-trations in the refined fuel and additional contamination may take place as a consequence of transporting the refined fuel through pipelines containing sulfur contaminants. Sulfur has a particularly corrosive effect on equipment such as brass valves, gauges and in-tank fuel pump copper commutators.
A commonly used technique for inhibiting corrosion cif copper, steel or copper alloys in fuel systems is by the use of corrosion inhibitors. These additives are either sulfur scavengers or metal deactivators that coat metal surfaces preventing sulfur components to react, with the metal. Many such corrosion inhibitars are known. Far example, U.S. Patent 3,663,561 discloses 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazoles which are stated to be useful as sulfur scavengers and U.S. Patent 5,035,720 relates to a corrosion inhibiting composi-tion comprising an oil-soluble adduct of a triazole and a basin nitrogen compound.
It would be desirable to have a copper corrosion inhibitor which would protect copper at low treat rates When exposed to a variety of fuels under different conditions and which would not 'produce high levels of insolublea or cause injector sticking in diesel engines.

This invention relates to a distillate fuel composition having improved copper corrosion properties which comprises a major amount of distillate fuel and an amount effective to grovide copper corrosion protection of a synergistic additive combination of (a) a 2,5-dihydrocarbyldithio-1,3,4-thiadiazole of the formula ~/ \S/ \S ~ R1 where Rl and R2 are independently hydrogen or R3S where R3 is a hydrocarbyl group containing 1 to 16 carbon atoms with the proviso that at least one of R1 and R2 is not hydrogen, and (b) an adduct of tolyltriazole and a basic nitrogen compound selected from the group consisting of polyamines, alkoxyamines, aryloxyamines and monoalkyleneamines.
In another embodiment, this invention concerns a method for reducing copper corrosion in a fuel delivery system or internal combustion engine by operating the fuel delivery system or internal combustion engine with the composition described above. Yet another embodiment involves a fuel additive concentrate containing the above additive combination.
Detained nescriotion of the Invent oar This invention concerns the discovery that a distillate fool containing a majar amount of distillate fuel and a minor amount of a synergistic combination of (a) 2,5-hydrocarbyldithio-1,3,4-thiadiazole and (b) an adduct of tolyltriazole and basic nitrogen compound can reduce copper corrosion in fuel delivery systems and internal combus-tion engines. The combination of components (a) and (b) unexpectedly _ __. .... I till ,,r . .

provides better protection from copper corrosion than either of the components alone.
In the additive combination noted above, component (a) is a thiadiazole of the formula R2S \S \SR1 where R1 and R2 are hydrogen or R3S, R3 is preferably a C1 to C10 hydrocarbyl group. The hydrocarbyl groups include aliphatic (alkyl or alkenyl) and alicylic groups which may be substituted with hydroxy, amino, vitro and the like. Examples of preferred R3 groups include methyl, ethyl, n- and iso-propyl, n-, sec- and tert-butyl, hexyl, cyclohexyl, octyl and decyl.
Preferred tolyltriazole adducts include the 1:1 adducts of tolyltriazole with fatty amines. Especially preferred fatty amines have the formula R4R5NR6 Where R4 and R5 are C1 to C4 hydrocarbyl groups which may be substituted with hydroxy, particularly C2 alkyl substituted with hydroxy and R6 is a Cg to C20 hydrocarbyl group, especially C12 to Clg alkyl or alkenyl. Examples of preferred adducts include the l:l adduct between tolyltriazole and bia(2-hydroxyethyl) oleylamine and between tolyltriazole and bis (2-hydroxyethyl) coco-amine.
The tolyltriazole adducts with polyamines, alkoxyamines, aryloxyamines and monoalkyleneamines may be prepared by the methods described in U.S. Patent 5,035,720. In general, the amine is heated to between 70°C and 100°C and tolytriazole added slowly to the heated amine with stirring. Tolyltriazole is added to amine in an approxi-mate 1:1 mole ratio. Upon completion of the reaction, the reaction mixture is cooled and may be used without further purification.
The distillate fuels of this invention will, in general, comprise a major amount of gasoline and a minor synergistic amount of the thiadiazole and the tolytriazole adduct. However, the precise /~
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amount and ratio of the thiadiazole and tolytriazole adduct can vary broadly. As such, only an amount effective or sufficient to reduce the formation of engine intake system deposits need be used. Typical-ly, however, the amount of the thiadiazole component will range from about 2 to about 30 ppmw, although greater amounts could be used.
Preferably, from about 2 to about 10 ppmw of the thiadiazole component will be present in the fuel. The amount of tolyltriazole adduct will generally range from about 8 to about 90 ppmw, preferably from about 8 to about 40 ppmw, based on fuel.
Other additives may be included in the fuel. examples of such additives include antiknock agents (e. g., tetraethyl lead), detergents or dispersants, demulsifiers, antioxidants and the like.
Although the tolyltriazole adducts and thiadiazoles used herein will generally be added to a distillate fuel, they may be formulated as a concentrate using an organic solvent (e. g., a hydro-carbon solvent, an alcohol solvent, or mixtures thereof) boiling in the range of about 165°C to about 400°C. Preferably, an aromatic hydrocarbon solvent (such as benzene, toluene, xylene, or higher boiling aromatics or aromatic thinners, and the like) is used.
Aliphatic alcohols containing from 3 to 8 carbon atoms (such as isopropanol, isobutylcarbinol, n-butanol, and the like), alone or in combination with hydrocarbon solvents, can also be used. The amount of thiadiazole in the concentrate will ordinarily be at least 10 wt%
and, .generally, will not exceed about 50 wt%. The amount of adduct of tolyltriazole and basic nitrogen compound will generally be between 30 wt% and 70 wt%. The amount of solvent will make up the balance of the eencantrate.
fihis invention will be further understood by reference to the following examples, which include a preferred embodiment of this invention.

f 1 2? ~.~6~~
Example 1 This example shows a comparison of copper corrosion between a w typical metal deactivator and the synergistic combination according to this invention. The corrosion test is ASTM D-130 which is described as follows.
A polished copper strip is immersed in 30 ml of sample contained in a clean, dry 25 by 150 mm test tube and.placed into a controlled temperature bath at 10011°C. After 3 hours, the copper strip is removed, washed, and compared with the ASTM Copper Strip Corrosion Standards.
The ratings correspond to the following descriptions of the appearance of the copper strip:
Ratina Description la Slight tarnish. Light orange, almost the same as a freshly polished strip.
lb Slight tarnish. Dar orange.
2a Moderate tarnish. Claret red.
2b Moderate tarnish. Lavender.
2c Moderate tarnish. Multicoloured with lavender blue or silver, or both, overlaid on claret red.
2d Moderate tarnish. Silvery.
2e Moderate tarnish. Brassy or gold.
3a Dark tarnish. Magenta overcast on brassy strip.
3b Dark tarnish. Multicoloured with red and green showing (peacock), but no gray.
4a~ Corrosion. Transparent black, dark grey or brown with peacock green barely showing.
4b Corrosion. Graphite or lusterless bleak.
4c Corrosion. Glossy or jet black.
Various samples of diesel fuels, including sour diesel fuels wero treated with Reomet~ 39 which is believed to be a 1-(dioctyl-amir.o) methyl tolyltriazole manufactured by Ciba-Geigy Corp. and a combination of 30 wt~ Elco~ 461 which is believed to be a diocty?.di-thio-1,3,4-thiadiazole manufactured by Elco Corp. and 70 wrt~
Petrolite~ 91-57676 which is believed to be a 1:1 adduct of tolyl-triazole and bis(2-hydroxyethyl)cocoamine manufactured by Petrolite Corp., arid tested copper The results fox corrosion using ASTMD-130.

are shown in Table 1.

Copper Corrosion (D-1301 Ratina Treat rate, Diesel Diesel 506 DieselDiesel 434 Additive m 1 506 +9 ma/1 S , 434 +9 mall S

-- 0 3a 4a 3b 4a Reomet 39 10 3a 3b 3b 3b 20 3a 3b 3b 3b 30 3a 3b 3b 3b 40 3a 3b 3b 3b 50 3a 3b 3b 4a 80 3a 3b 3b 3b Elco 461 10 3a 3b 3b 3b +91-57676 20 3b 3a 3b 30 lb 3b 3a 4a 40 lb lb lb lb This data demonstrates the combinationof that Elco~

plus Petrolite~ 91-57676is capableof achieving corrosion a rating of la/lb at the mg/1 cannot even 30 to 40 treat rate whereas Reamet at twice the te.
treat ra Example 2 This example demonstrates the synergistic action of a this-diazole plus tolyltriazole adduct versus either component acting alone. Table 2 is a comparison of Petrolite~ 91-57676 alone, Elcog alone and a combination of 30 wt~ Elco~ 461 plus 70 wt~ Petrolite~
1-57676 using the copper corrosion test ASTM D-130 described in Example 1.

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_Co xaper CorrosionRatina (D-130) Treat Rate Diesel 295 Additive mall ~9 ma/1 S

-- 0 4a 91-57676 10 4a 20 4a 30 4a 40 4a Elco 461 5 4a 4a 2d lb lb wt~ Elco 10 4a 70 wt~ 91-5767620 4a 30 lb lb Petrolite~ 91-57676 alone cannot achieve a la/ib rating over the treat rate studied. Elco~ 461 is capable of achieving a 1a/1b rating at a treat rate of 20 mg/1. The combination according to invention shown in Table 2 can achieve a la/lb rating at a total 30 mg/1 treat rate.
This 30 mg/1 treat rate is made up of 9 mgjl of Eloo'~ 461 and 21 mg/1 of Petrolite~ 91-57676. Thus, the combination achieves a comparable rating at a treat rate which is less than one-half the treat rate of either component alone.
Example 3 This example shows that the synergistic combination of the invflntion produces less insolubles when compared to a single component alone. The test used to determine insolubles is ASTM D-2274 which is described as follows A 350 ml volume of filtered middle distillate fuel is aged at 95°C for 16 hours while oxygen is bubbled through the sample at a rate of 3 L/h. After aging, the sample is cooled to approximately room temperature before filtering to obtain the filter-able insolubles quantity. Adherent insolubles are then removed from the oxidation cell and associated glassware with trisolvent. The trisol~~ent is evaporated to obtain the quantity of adherent insol-ublea. The sum of the filterable and adherent insolubles, expressed as milligrams per 100 ml, is reported as total insolubles.
The results are summarized in Table 3.
TABZ.E 3 Diesel Base Diesel Base Diesel +100 mg/1 +30 mg/1 Eloo 461 Properties, Base Elco 461461 +70 mall 91-57676 Filt Insol, mg/1000.68 1.3 054 ml Adh Inaol, mg/100 0.09 0.2 0.11 ml Total Insol, mg/1000.77 1.5 0.65 ml Colour Initial < 2.0 < 2.0 < 2.0 Colour Final < ~.5 < 3.0 < 3.0 As shown in Table 3, the combination of Elco~ 461/Petrolite~ 91-57676 produces less insolubles than Elcog 461 alone at equivalent treat rate.
Example 4 An important test for fuel performance in diesel engines is an injector sticking test. This is a qualitative test which evaluates fuel performance in a diesel engine under a given set of engine operating conditions with the only variable being the fuel under evaluation. Each diesel injector is eisuall;y inspected for stickiness after each 20 hr. cycle of a four cycle test protocol. The cambina-tion of 30 wt~ Elco~' 461j70 wt~ Petrolite~ 91-57676 passed this. teat at 100 mg/1 treat rate whereas Elcoe 461 at the same treat rate Exiled.

Claims (7)

1. A distillate fuel composition which comprises a major amount of distillate fuel and an amount effective to provide copper corrosion protection of a synergistic additive combination of (a) a 2,5-dihydrocarbyldithio-1,3,4-thiadiazole of the formula wherein R1 and R2 are independently R3S or H where R3 is a hydrocarbyl group containing from 1 to 16 carbon atoms with the proviso that at least one of R1 and R2 is not hydrogen, and (b) a 1:1 adduct of tolyltriazole and a fatty amine of the formula R4R5NR6 where R4 and R6 are C1 to C4 hydrocarbyl groups or said groups substituted by OH and R6 is a hydrocarbyl group of from 8 to 20 carbon atoms.

2. The composition of claim 1 wherein R3 is a hydrocarbyl group of from 1 to 10 carbon atoms.

3. The composition of claim 1 wherein R4 and R5 are hydroxyethyl groups.

4. The composition of claim 1 wherein the tolyltriazole adduct is a 1:1 adduct of tolyltriazole with bis(2-hydroxyethyl) oleylamine or with bis(2-hydroxyethyl)cocoamine.

5. The composition of claim 1 wherein the amount of component (a) is from 2 to 30 ppmw and the amount of component (b) is from 8 to 90 ppmw.

6. A method for reducing copper corrosion in a fuel delivery system or internal combustion engine which comprises operating the fuel delivery system or internal combustion engine with a fuel containing an effective amount to reduce copper corrosion of the synergistic combination of any one of claims 1 to 5.

7. An additive concentrate suitable for blending with a distillate fuel to provide copper corrosion protection which comprises a solvent and from 10 wt% to 50 wt% based on solvent of a 2,5-dihydro-carbyldithio-1,3,4-thiadiazole of the formula wherein R1 and R2 are independently R3S or H where R3 is a hydrocarbyl group containing from 1 to 16 carbon atoms with the proviso that at least one of R1 and R2 is not hydrogen, and from 30 wt% to 70 wt%
based on solvent of a 1:1 adduct of tolyltriazole and a fatty amine of the formula R4R5NR6 where R4 and R5 are C1 and C4 hydrocarbyl groups and R6 is a hydrocarbyl group of from 8 to 20 carbon atoms.