Method of limiting chemical degradation due to nitrogen dioxide contamination

Abstract

To provide an additive composition for limiting and a method of limiting chemical degradation of hydrocarbonaceous liquids due to nitrogen dioxide contamination in high-temperature operation.SOLUTION: An additive composition for hydrocarbonaceous liquids comprises an ionic liquid and a detergent additive. The ionic liquid comprises (i) one or more organic cations each comprising a central atom or ring system bearing a cationic charge and multiple pendant hydrocarbyl substituents, and (ii) one or more halogen-, sulfur- and boron-free organic anions each comprising one or more hydrocarbyl groups and one or more heteroatom-containing functional groups bearing a localized or delocalized anionic charge. The detergent additive comprises, as an active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts. Optionally, the additive composition further comprises a carrier liquid or diluent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for limiting the chemical decomposition of hydrocarbon liquids due to nitrogen dioxide contamination during high temperature operation. The method basically involves adding to the hydrocarbon liquid an additive composition comprising a selected ionic liquid and a detergent additive, the combination of the ionic liquid and detergent acting to inhibit the nitration of the hydrocarbon liquid by nitrogen dioxide which initiates the decomposition. [Background technology]

[0002] Hydrocarbon liquids are used as operating fluids in a variety of machinery applications, particularly as lubricants, protectants, hydraulic fluids, greases, and heat transfer fluids for engineering components and devices. The composition and properties of such liquids are selected according to their intended use, and the ready availability of high molecular weight hydrocarbon species allows such fluids to be formulated for high temperature operation, particularly above 100°C, where aqueous fluids are unusable. Such hydrocarbon liquids may typically be obtained from petroleum or synthetic sources, or from the processing of renewable materials such as biomaterials. In particular, hydrocarbon-based lubricants and hydraulic fluids have become standard in a variety of applications, including automotive and power transmission fluids such as engine lubricants. The fundamental performance characteristic of an operating fluid is its ability to retain its beneficial properties over its operational life. Operation under severe conditions places physical and chemical strain on the fluid, and limiting the resulting fluid decomposition is a major consideration in fluid selection and formulation. Operating fluids must typically meet many performance requirements during development and certification related to maintaining operational life, and candidate fluids are subjected to testing under relevant operating conditions that promote decomposition. High operating temperatures and the presence of chemically reactive contaminants place increased demands on hydrocarbon liquids. High bulk liquid temperatures and accumulation of reactive contaminants can accelerate decomposition reactions, severely reducing operational life and rendering the liquid inadequate to operate or protect surrounding machinery. There is a general need in the art to improve the service life of hydrocarbon fluids, particularly lubricants, operating at elevated bulk temperatures by improving their resistance to chemical degradation in the bulk under operating conditions.

[0003] The decomposition of hydrocarbon fluids, especially at elevated bulk temperatures, has typically been referred to in the art as "oxidation." This oxidation is based on the conventional understanding that the chemical reactions responsible for decomposition primarily involve the reaction of aged hydrocarbon species with oxygen via a free radical pathway involving peroxides formed in situ during operation. The accumulation of these aged hydrocarbon species over time accelerates fluid decomposition, degrading bulk fluid properties and operational performance. A variety of additives, traditionally referred to as "antioxidants," have been proposed in the art. Antioxidants inhibit this oxidation pathway and include hydrocarbon-soluble hindered phenols and amines, slowing the eventual accumulation of oxidative degradation associated with fluid aging during operation.

[0004] However, research by the applicant has characterized another chemical decomposition pathway that occurs in freshly prepared hydrocarbon fluids free of aging components. This decomposition is initiated not by reaction with oxygen or peroxides, but by the direct chemical action of nitrogen dioxide at high temperatures, which has been introduced into the fluid through contamination during operation. Nitrogen dioxide initiates chemical decomposition through a nitration reaction with the hydrocarbon fluid, and this reaction has been found to significantly destroy the fluid, a process that begins while the fluid is still fresh. Nitrogen dioxide can also oxidize to nitric acid in the bulk fluid environment, causing acidic attack on the fluid and the mechanical equipment designed to protect it. As a result, there is a specific need to limit the decomposition effects of nitrogen dioxide contamination in hydrocarbon fluids at high temperatures. This decomposition effect can cause decomposition early in the operational life and can also exacerbate problems caused by traditional oxygen-driven oxidation. Such contamination by nitrogen dioxide occurs when hydrocarbon fluids are exposed to sources of nitrogen dioxide during operation. Nitrogen dioxide (NO) is formed, for example, during combustion reactions, through the reaction of naturally occurring nitrogen in air with oxygen when exposed to high temperatures, frequently through the intermediate formation of nitric oxide (NO). Nitrogen dioxide is also a product of combustion of fuels derived from petroleum or many biological sources. Both petroleum and biological sources contain large amounts of bound nitrogen, which is released as nitrogen dioxide upon complete combustion and can become incorporated into operating fluids that come into contact with it. Such exposure is particularly prevalent in combustion devices, such as internal combustion engines, which produce nitrogen dioxide and are lubricated by hydrocarbon fluids exposed to exhaust gases; particularly in crankcase lubricating oil, which resides on engine surfaces in the cylinder area and in direct contact with exhaust gases, and which directs nitrogen dioxide over piston rings and into the crankcase oil reservoir via blow-by exhaust gases, where it is incorporated with the lubricant. Modern engine and aftertreatment developments aimed at improving engine fuel efficiency and minimizing carbonaceous particulate matter emissions have resulted in higher combustion temperatures, which produce higher levels of nitrogen dioxide in engine exhaust gases due to an effect known as "NOx-particulate exchange." Higher engine temperatures also increase bulk lubricant operating temperatures, creating conditions for increased nitrogen dioxide-initiated chemical decomposition. Also, modern trends have focused on improving fuel economy in internal combustion engines, leading to designs that reduce internal friction by increasing the gap between the piston rings and the back of the cylinder, resulting in a self-propelled engine where the piston rings blow more exhaust gases into the crankcase, entraining the exhaust gases in the bulk engine lubricant.

[0005] Thus, hydrocarbon fluids that experience nitrogen dioxide contamination during high-temperature operation face particular challenges due to chemical nitration pathways that operate early in the fluid's life and are not initiated by traditional oxidation of hydrocarbons. This challenge is particularly acute in the case of engine lubricants, where various engineering measures have increased the extent of nitrogen dioxide uptake in the bulk lubricant at high operating temperatures. Applicant has determined that the resulting nitration pathway is particularly pronounced at bulk fluid temperatures between 60 and 180°C, and particularly severe at bulk fluid temperatures between 110 and 160°C, temperatures that are more pronounced in crankcase lubricants used under severe operating conditions or in modern high-running engine designs, thereby exacerbating the impact of this chemical pathway on lubricant degradation. The present invention provides a solution to this problem through the formulation of a combination of selected ionic liquids and detergent additives that have a specific synergistic ability to deactivate nitrogen dioxide and thereby inhibit nitrification of hydrocarbon liquids. Through this unexpected action, the selected combination of ionic liquids and detergent additives limits the chemical decomposition that initiates nitrification and improves the operational life of hydrocarbon liquids. The present invention also unexpectedly controls oxidation in oils, particularly in the presence of dispersant additives and under nitrogen dioxide polluting conditions where the dispersant neutralizes the effectiveness of conventional phosphorus-based antioxidants.

[0006] One of the physical consequences of chemical decomposition in hydrocarbon-based operating fluids is an increase in fluid viscosity during operation. This increase in viscosity can cause the fluid to fail to meet specified viscosity standards, potentially resulting in the fluid having to be replaced sooner. The formulation of an additive composition comprising a combination of an ionic liquid and a detergent additive as defined in the present invention provides the advantage of limiting viscosity increase during operation and limiting the resulting service life limitations. Many hydrocarbon fluids, particularly lubricants such as engine lubricants, are formulated to control increased acidity caused by oxidation processes resulting from the formation of acid species in the fluid, and subsequent acid corrosion or wear. Therefore, controlling the accumulation of acid species over their operational life is an added benefit for such fluids. The formulation of an additive composition comprising a combination of an ionic liquid and a detergent additive as defined in this invention provides the advantage of improved control of acid accumulation in the fluid, with the additional benefit of allowing the formulator to formulate an improved operating fluid.

[0007] Thus, the combination of ionic liquids and detergent additives as defined in this invention provides advantages over conventional antioxidants and other ionic liquids previously considered in the art for use as additives in hydrocarbon fluids, and broadens the range of properties that enhance operating fluid performance and service life. The co-presence of detergent additives provides better performance than the beneficial effects of a given ionic liquid alone, improving service life and other benefits of this invention. In a preferred embodiment, a combination of ionic liquid and detergent additive is formulated in conjunction with an ashless dispersant additive, and this three-component combination provides particularly advantageous control of nitrification resulting from nitrogen dioxide pollution while allowing the use of dispersants to benefit from their effects. In U.S. Patent No. 8,278,253, the oxidation resistance of lubricating oils is enhanced by the addition of additive amounts of ionic liquids. From the description of this invention and Example 1, it is clear that the method is focused on reducing oxidation by hydroperoxides, rather than nitrogen dioxide-induced decomposition, which is the focus of this invention. While a wide variety of cations and anions are separately listed as possible components of ionic liquids, the preferred anions and all of the anions in the examples are fluorine-containing non-aromatic structures, most of which also contain boron. This document does not disclose the specific cation-anion combinations required for the ionic liquids of this invention, nor does it teach the benefits of inhibiting nitrogen dioxide-induced nitration of new, unaged lubricants, or improving other related properties.

[0008] WO 2008 / 075016 relates to ionic liquid additives for non-aqueous lubricating oil compositions, which are intended to reduce wear and / or modify frictional properties and are defined as non-halogenated, non-aromatic ionic liquids. - has an ionic head group containing at least one oxygen atom and attached to at least one alkyl or alicyclic hydrocarbyl group. This reference also fails to disclose the specific cation-aromatic anion combinations required for the ionic liquids of the present invention, nor does it teach the benefits of inhibiting nitration by nitrogen dioxide of new, unaged fluids, or improving other related properties. WO 2013 / 158473 relates to lubricant compositions containing ionic liquids and methods of using such compositions to minimize deposit and sludge formation in internal combustion engines. The study focuses on high-temperature deposit formation that occurs after pre-test aging of lubricating oils, where a fresh lubricant is blended with a quantity of used lubricant and sparged with a dry air / nitrogen dioxide mixture. The deposit-generating process is then carried out on a metal surface heated to at least 200°C, optimally 320°C, while exposed to simulated exhaust gases. The ionic liquid contains a pair of nitrogen-containing cations and anions represented by the structure YCOO(-), where Y is alkyl or aromatic, preferably an alkyl or alkoxyl functional group having 1 to 50 carbon atoms, or a benzene group, or an alkylated benzene group where the alkyl group(s) have 1 to 10 carbon atoms. This document does not disclose the specific cation-anion combinations of the ionic liquids formulated in the present invention, nor does it teach the benefits of inhibiting nitration by nitrogen dioxide of new, unaged fluids at bulk liquid temperatures below 200°C, or improving other related properties.

[0009] U.S. Patent Publication No. 2010 / 0187481 relates to the use of ionic liquids to improve the lubricating effect of synthetic, mineral, or natural oils. The invention discloses that the resulting lubricant composition is protected from thermal and oxidative attack. The ionic liquids are said to be superior to phenolic or amine antioxidants as thermal and oxidative stabilizers due to their solubility in organic systems or their extremely low vapor pressure. Preferred anions of the ionic liquids are highly fluorinated, such as bis(trifluoromethylsulfonyl)imide, due to their high thermal stability. The patent makes no mention or explicit mention of controlling nitrogen dioxide decomposition.

[0010] Applicant has now discovered that the incorporation of a combination of an ionic liquid containing a selected cation and a selected anion free of halogens, sulfur, and boron; and a detergent additive containing one or more hydrocarbyl-substituted neutral or overbased metal salts as active ingredients in dosage amounts provides a method for inhibiting nitration of hydrocarbon fluids due to nitrogen dioxide contamination at high temperatures and for limiting chemical degradation of hydrocarbon fluids even when new and not operationally aged. This method extends the life of operating fluids that encounter such contamination and provides further advantages over the prior art, as detailed herein. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 8,278,253 [Patent Document 2] International Publication No. 2008 / 075016 [Patent Document 3] International Publication No. 2013 / 158473 [Patent Document 4] US Patent No. 2010 / 0187481 [Patent Document 5] US Patent No. 2008 / 0251759 [Patent Document 6] U.S. Patent No. 6,153,565 [Patent Document 7] U.S. Patent No. 6,281,179 [Patent Document 8] U.S. Patent No. 6,429,178 [Patent Document 9] U.S. Patent No. 3,202,678 [Patent Document 10] U.S. Patent No. 3,154,560 [Patent Document 11] U.S. Patent No. 3,172,892 [Patent Document 12] U.S. Patent No. 3,024,195 [Patent Document 13] U.S. Patent No. 3,024,237 [Patent Document 14] U.S. Patent No. 3,219,666 [Patent Document 15] U.S. Patent No. 3,216,936 [Patent Document 16] U.S. Patent No. 3,087,936 [Patent Document 17] U.S. Patent No. 3,254,025 [Patent Document 18] European Patent Application Publication No. 090 642 [Patent Document 19] U.S. Patent No. 3,113,986 [Patent Document 20] U.S. Patent No. 3,700,633 [Patent Document 21] U.S. Patent No. 3,634,595 [Patent Document 22] U.S. Patent No. 3,670,054 [Patent Document 23] U.S. Patent No. 3,700,633 [Patent Document 24] U.S. Patent Reissue No. 27,145 [Non-patent literature]

[0012] [Non-Patent Document 1] Coultas, D.R. "The Role of NOx in Engine Lubricant Oxidation," SAE Technical Paper, 2020, Issue 2020‐101427, Digital Object Identifier (doi):10.4271 / 2020‐01‐1427 [Non-patent document 2] "Engine Oil Licensing and Certification System (ELOCS)" published by the American Petroleum Institute (API), Industry Services Division, December 1996, 14th Edition, Appendix 1, December 1998 Summary of the Invention

[0013] In a first aspect, the present invention provides an additive composition for hydrocarbon liquids, the additive composition comprising an ionic liquid and a detergent additive, the ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups, respectively, having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts; the additive composition further comprises a carrier fluid or diluent. In a second aspect, the present invention provides a hydrocarbon liquid composition comprising a predominant amount of a hydrocarbon liquid and minor amounts of an ionic liquid and a detergent additive, the ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as the active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts.

[0014] In a third aspect, the present invention provides a method for limiting chemical decomposition of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180° C., said decomposition being initiated by nitration of the liquid resulting from nitrogen dioxide contamination during operation, said method comprising: preparing or obtaining a freshly prepared hydrocarbon liquid suitable for operation at a bulk liquid temperature of 60 to 180°C and free of aging components and nitrogen dioxide contamination; and adding an ionic liquid and a detergent additive to the hydrocarbon liquid prior to operation at a bulk liquid temperature of 60 to 180°C, wherein the ionic liquid: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; thereafter adding said ionic liquid and detergent active ingredient in amounts synergistically effective to inhibit nitration of the hydrocarbon liquid while operating at a bulk liquid temperature of 60 to 180°C in the presence of nitrogen dioxide contamination; and subjecting said hydrocarbon liquid to operation, whereby the ionic liquid and detergent additives limit chemical decomposition of the resulting liquid. Includes:

[0015] In a fourth aspect, the present invention provides the use of an ionic liquid in combination with a detergent additive, said ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; Limiting the chemical decomposition of hydrocarbon liquids initiated by nitration of hydrocarbon liquids resulting from nitrogen dioxide contamination during operation at bulk liquid temperatures between 60 and 180°C; The ionic liquid and detergent additives are added to an aging component- and nitrogen dioxide-free hydrocarbon liquid prior to operation, and the ionic liquid and detergent active ingredients then inhibit nitrification of the hydrocarbon liquid during operation at bulk liquid temperatures of 60-180°C in the presence of nitrogen dioxide contamination.

[0016] In a fifth aspect, the present invention provides the use of a detergent additive comprising, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts, for the purpose of enhancing the efficacy of the ionic liquid additive for inhibiting nitration of hydrocarbon liquids due to nitrogen dioxide contamination at operation at bulk liquid temperatures between 60 and 180°C, wherein the ionic liquid: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive is added to the hydrocarbon liquid containing the ionic liquid additive prior to operation at bulk liquid temperatures between 60 and 180°C and exposure to nitrogen dioxide contamination.

[0017] A further aspect of the present invention is the use of an ionic liquid in conjunction with a detergent additive in a hydrocarbon liquid, said ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; Said use is: (a) inhibiting the chemical oxidation of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180°C in the presence of nitrogen dioxide contamination; and / or (b) inhibiting the increase in kinematic viscosity of hydrocarbon liquids during operation at bulk liquid temperatures between 60°C and 180°C in the presence of nitrogen dioxide contamination; and / or (c) inhibiting the increase in total acid number of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180°C in the presence of nitrogen dioxide contamination; With the aim of; In each use, the ionic liquid and detergent additives are added to a hydrocarbon liquid that is free of aging components and nitrogen dioxide prior to operation, and the ionic liquid and detergent then inhibit the effects of aging components and nitrogen dioxide in the hydrocarbon liquid during operation at bulk liquid temperatures of 60-180°C in the presence of nitrogen dioxide contamination.

[0018] Preferably, the compositions of the first and second aspects further comprise an ashless dispersant additive, and preferably, the methods and uses of each of the remaining aspects revolve around the addition of an ashless dispersant additive. Preferred embodiments of these various aspects of the invention are described below. This specification also refers to the following figures: [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 3 shows end-of-test kinematic viscosity results obtained from lubricating oil compositions containing ionic liquids and other additives in the tests detailed in Example 3.2 below; [Figure 2] FIG. 3 shows the total acid number at the end of the test for lubricating oil compositions containing ionic liquids in the tests detailed in Example 3.3 below. DETAILED DESCRIPTION OF THE INVENTION

[0020] It is to be understood that the various essential, as well as optional and conventional, ingredients employed may react under conditions of preparation, storage, or use, and that the present invention also provides products obtainable or obtained as a result of any such reactions. Further, it is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. It is also to be understood that preferred features of each aspect of the invention are to be considered preferred features of every other aspect of the invention, and thus preferred and more preferred features of one aspect of the invention may be independently combined with other preferred and / or more preferred features of the same or different aspects of the invention. The importance of nitrogen dioxide decomposition in new lubricants at high temperatures has recently been reported by the present applicant in a paper cited as Coultas, DR, "The Role of NOx in Engine Lubricant Oxidation," SAE Technical Paper, 2020, Issue 2020-101427, Digital Object Identifier (doi):10.4271 / 2020-01-1427. In its preface, the paper states that "the primary mechanism by which NOx decomposes lubricants is through participation in free-radical nitro-oxidation reactions." The following equation shows that nitrogen dioxide initiates the process by abstracting a proton from a liquid hydrocarbon species, setting off a series of reactions involving other species, resulting in the chemical decomposition of the hydrocarbon liquid. Nitrogen dioxide also plays a prominent role further down this degradation pathway by reacting with RO radicals to form hydrocarbon nitrate esters, represented by the formula RONO2. These hydrocarbon nitrate esters accumulate in the lubricant, forming a reservoir of nitrate esters. At elevated operating temperatures, these nitrate esters gradually dissociate, releasing the trapped RO radicals and forming the characteristic nitrate ester "volcano curve" depicted in Figure 14 of this paper. This rapid dissociation of nitrate esters to free radicals accelerates the chemical destruction of hydrocarbon species in the liquid. This multiple reaction of nitrogen dioxide, including both the initial proton abstraction and the subsequent dissociation of the formed nitrate esters, is referred to herein as the "nitrification" of the hydrocarbon liquid.

[0021] Applicant has determined that the initiation of this nitrification reaction pathway via proton abstraction by nitrogen dioxide, and the formation and dissociation of nitrate ester reservoirs upon further action of nitrogen dioxide, are a function of elevated bulk fluid temperatures. The initiation of the nitrification reaction sequence is underway at 60°C and accelerated at temperatures above 80°C. Nitrate ester formation is significant in the 110-180°C range, with the rate of nitrate ester dissociation increasing from 130°C. In the 110-160°C temperature range, nitrate ester formation and dissociation are most significant, further promoting the chemical decomposition of hydrocarbon fluids. Therefore, the trend toward increasing bulk fluid (sump) temperatures (to temperatures above 130°C) in modern engine lubricants increases the net result of nitrogen dioxide contamination, making these engine lubricants more susceptible to this form of decomposition. Without being bound by any particular theory, Applicant believes from technical research that the ionic liquids and detergent additives incorporated herein possess a particular synergistic ability to deactivate nitrogen dioxide present as a contaminant in hydrocarbon fluids, thereby inhibiting the nitrogen dioxide from reacting with hydrocarbon fluid species and initiating decomposition via proton abstraction, initiating the nitrification pathway. Furthermore, Applicant further inhibits the nitrogen dioxide from reacting to form nitrate esters, which produce a volcano-shaped curve at higher temperatures, and the release of radicals that lead to further decomposition.

[0022] In particular, applicants have discovered that the co-addition of a detergent additive containing as an active ingredient one or more hydrocarbyl-substituted neutral or overbased metal salts increases the efficacy of certain ionic liquids in deactivating nitrogen dioxide and further inhibits nitration in hydrocarbon liquids subjected to high temperatures and nitrogen dioxide contamination. This beneficial effect is found to result from the combination of the ionic liquid and detergent in the hydrocarbon liquid, which reduces nitration levels during operation. Additionally, Applicants have discovered that the preferred ionic liquids formulated herein (including preferred aromatic carboxylate salt embodiments of the anion) when combined with certain cleaning agents of the present invention provide superior affinity for nitrogen dioxide compared to other ionic liquids, particularly at comparable viscosities. Applicants have also demonstrated that the inclusion of the preferred ionic liquids correspondingly improves the ability of the present invention to inhibit nitration of hydrocarbon liquids under operating conditions subject to high temperatures and inhibit the increase in bulk liquid acidity over time. Other advantages of the operating conditions of the present invention with respect to inhibition of oxidation, viscosity increase, and total acid number are demonstrated in the working examples described later in this specification.

[0023] Ionic liquid blended in all aspects of the present invention Ionic liquids are conventionally understood to be ionic compounds that contain one or more cation-anion pairs and exist in liquid physical form at commercially useful temperatures. All aspects of the present invention incorporate certain ionic liquids that include: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge. The one or more cations (i) carry a cationic (positive) charge and contain multiple hydrocarbyl substituents that impart organophilic properties to the ionic liquid, allowing it to be readily miscible with hydrocarbon-based bulk liquids. As used herein, the term "hydrocarbyl substituent" refers to a group containing hydrogen and carbon atoms, each directly bonded to the remainder of the compound via a carbon atom. The group may contain one or more atoms other than carbon and hydrogen (i.e., heteroatoms), provided that the essentially hydrocarbyl character of the group, i.e., oxygen and nitrogen atoms, is not affected; such groups include amino, nitro, and alkoxy groups. Preferably, however, the hydrocarbyl group, unless otherwise specified, consists essentially of, and more preferably consists of, hydrogen and carbon atoms. Preferably, the hydrocarbyl group is or includes an aliphatic hydrocarbyl group. The term "hydrocarbyl" encompasses the term "alkyl," as conventionally used herein. Preferably, the term "alkyl" refers to a radical of carbon and hydrogen (e.g., C1-C6). 30 For example, C4~C 20 The term "alkyl" refers to a group (a cyclic group). An alkyl group in a compound is typically directly attached to the compound via a carbon atom. Unless otherwise specified, an alkyl group can be straight-chain (i.e., unbranched) or branched, and can be cyclic, acyclic, or partially cyclic / acyclic. An alkyl group can include straight-chain or branched acyclic alkyl groups. Representative examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, dimethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, and triacontyl. A substituted alkyl group is an alkyl group in which a hydrogen or carbon is replaced with a heteroatom (i.e., not H or C) or a heteroatom-containing group. The term "substituted" generally means that a hydrogen has been replaced with a carbon or heteroatom containing group.

[0024] In a first embodiment, one or more of the cations (i) in the ionic liquid may contain nitrogen. In this embodiment, each cation (i) is preferably a hydrocarbyl-substituted ammonium cation or a hydrocarbyl-substituted alicyclic or aromatic ring system incorporating nitrogen and bearing a cationic charge. In this first embodiment of the cation, each cation (i) is preferably a hydrocarbyl-substituted ammonium cation, preferably a tetrahydrocarbyl-substituted ammonium cation. In this embodiment, the hydrocarbyl group is preferably an alkyl group. Suitable alkyl groups as substituents on such ammonium cations include linear or branched alkyl groups having 1 to 28 carbon atoms, e.g., 4 to 28, preferably 6 to 28, and more preferably 6 to 14 carbon atoms. Particularly suitable alkyl substituents on such phosphonium cations include hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, particularly n-alkyl groups herein. Preferably, at least one of the alkyl substituents contains at least 10 carbon atoms and is selected from the examples above. Alkyl substituents with fewer carbon atoms may also be present, such as methyl groups. Most preferably in this embodiment, each cation (i) is a tetrabutylammonium cation, i.e., a cation bearing four butyl groups as substituents, and these substituents are preferably linear groups. Such cations are sometimes known in the art by the abbreviation "N4444," where each digit represents the number of carbon atoms in four butyl groups (4,4,4,4). Other most preferred examples of cations include tetraoctylammonium (N8888), trihexyltetradecylammonium (N66614), and trimethyletradecyl (N11114), or trimethylhexadecyl (11116) ammonium.

[0025] However, in a second, more preferred embodiment of the cations, each cation (i) of the ionic liquid does not contain nitrogen. This embodiment of the ionic liquid has been found to be more advantageous in the present invention. The ionic liquid also contributes to reducing nitrogen dioxide emissions during consumption, for example, when the hydrocarbon liquid itself is subjected to combustion, for example, when lubricating oil is consumed in an engine. In this second embodiment, it is further preferred that each cation (i) of the ionic liquid comprises a tetrahydrocarbyl-substituted central atom or ring system bearing a cationic charge. The hydrocarbyl groups may be the same or different and may be linear, branched, or cyclic. The hydrocarbyl groups are typically alkyl groups (e.g., linear or branched alkyl groups). In embodiments, the alkyl groups are the same alkyl, such as linear or branched alkyl groups having from 1 to 28 carbon atoms, e.g., from 4 to 28, preferably from 6 to 28, and more preferably from 6 to 14 carbon atoms. Particularly suitable alkyl substituents for such cations include butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, particularly n-alkyl groups herein. Most preferably, each cation (i) of the ionic liquid is a phosphorus-containing cation.

[0026] In this embodiment, each cation (i) is preferably an alkyl-substituted phosphonium cation, ideally a tetraalkyl-substituted phosphonium cation. Suitable alkyl groups as substituents on such phosphonium cations include linear or branched alkyl groups having 1 to 28 carbon atoms, e.g., 4 to 28, preferably 6 to 28, and more preferably 6 to 14 carbon atoms. Particularly suitable alkyl substituents on such phosphonium cations include hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, particularly n-alkyl groups herein. Preferably, at least one of the alkyl substituents contains at least 10 carbon atoms and is selected from the examples above. Most preferably, each cation (i) is a trihexyltetradecylphosphonium cation, i.e., a cation bearing three hexyl and one tetradecyl groups as substituents, which are preferably straight-chain alkyl groups. Such groups are sometimes known in the art by the abbreviation "P66614," where the numbers represent the carbon atoms in the three hexyl and one tetradecyl groups (6, 6, 6, 14), respectively. The one or more halogen-, sulfur-, and boron-free anions (ii) each contain one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge. The one or more anions (ii) may contain nitrogen atoms, particularly in the form of nitrates or nitrogen-containing organic ring structures, although preferably each anion (ii) is nitrogen-free. In a preferred embodiment, one or more anions (ii), preferably each anion (ii), comprises a carboxylate functional group, which group carries an anionic charge. In a first embodiment of the carboxylate salt, one or more hydrocarbyl groups attached to the carboxylate group are aliphatic groups, preferably consisting of carbon and hydrogen atoms, more preferably alkyl groups, such as C3-C27 alkyl groups, preferably C5-C17 alkyl groups, preferably n-alkyl groups. Such preferred anions (ii) include, in particular, hexanoate, octanoate, decanoate, dodecanoate, tetradecanoate, hexadecanoate, and octadecanoate. Such carboxylate anions (ii) may advantageously contain further heteroatom-containing functional groups, preferably oxygen-containing functional groups, such as hydroxy groups.

[0027] In a second, more preferred embodiment of the carboxylate salt, one or more anions (ii), more preferably all anions (ii), comprise a hydrocarbyl group that is an aromatic ring bearing at least two substituted functional groups containing heteroatoms, which are conjugated to the aromatic ring, and this conjugated system carries an anionic (negative) charge. The term "conjugated" is used herein in its traditional chemical sense, meaning that these substituted functional groups are directly bonded to the aromatic ring, with one or more p-orbitals of one or more atoms contained within each of these functional groups connecting to the p-orbitals of the adjacent aromatic ring and participating in the delocalized electron cloud of the aromatic ring. It is believed that anions of this preferred configuration have a particularly high affinity for nitrogen dioxide and can bind to it in a manner that significantly reduces their reactivity with hydrocarbon compounds. The aromatic ring contains carbon and, optionally, one or more heteroatoms, such as phosphorus, nitrogen, or oxygen. However, each anion (ii) of the ionic liquid preferably does not contain nitrogen. Such ionic liquids are more advantageous in the present invention, as they have been found to be unable to contribute to the formation of nitrogen dioxide in environments where a portion of the ionic liquid is consumed by combustion, such as in an engine lubricant environment.

[0028] In a first advantageous form of this preferred embodiment of the anion, the aromatic ring of each anion (ii) has two conjugated substituted functional groups containing heteroatoms, and the system has an anionic (negative) charge. This feature is preferably such that the aromatic ring of each anion (ii) of the ionic liquid has a carboxylate group and another heteroatom-containing functional group directly bonded to the aromatic ring, and the system has an anionic charge. More preferably, the heteroatom(s) in both of these functional groups consist of oxygen atoms. More preferably, the functional groups are located on adjacent ring carbon atoms in an "ortho" configuration to each other on the aromatic ring.

[0029] In this embodiment of the anion, each anion (ii) is highly preferably a disubstituted benzene ring having a carboxylate group and a second heteroatom-containing functional group containing only oxygen as the heteroatom, with these two groups preferably positioned in an "ortho" configuration relative to one another on the aromatic ring. Preferably, the second functional group is a hydroxyl group, forming a hydroxybenzoate anion (ii). Most preferably, the one or more anions (ii) of the ionic liquid are one or more salicylate anions, i.e., anions formed from the deprotonation of salicylic acid.

[0030] In a more advantageous second form of this preferred embodiment of the anion, the aromatic ring of each anion (ii) of the ionic liquid itself bears the substituents of the advantageous first form of the anion, preferably the substituents of the previous two paragraphs, and further bears one or more hydrocarbyl substituents that impart additional organophilic properties to the ionic liquid, making it more readily miscible with hydrocarbon-based bulk liquids. The hydrocarbyl substituent(s) added to the aromatic ring of the anion of this second embodiment are as defined above. Preferably, these substituent(s) are alkyl substituents. Suitable alkyl groups include straight- or branched-chain alkyl groups having 6 or more carbon atoms, preferably 6 to 28, more preferably 6 to 14 carbon atoms. Particularly suitable alkyl substituents include hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl groups, and particularly herein n-alkyl groups.

[0031] The aromatic ring of anion (ii) of this second embodiment may have a single or multiple alkyl substituents. The resulting ionic liquid may comprise a mixture of anions (ii) differing in the number and / or location of alkyl substituents. Preferably, at least one of the alkyl substituents has at least 10 carbon atoms and is selected from the examples above. More preferably, the aromatic ring of each anion (ii) in the ionic liquid has one or more linear or branched alkyl substituents with more than 10 carbon atoms. In a second more preferred embodiment of the anion, the one or more anions (ii) are hydrocarbyl-substituted hydroxybenzoates, preferably of the following structure: [ka] wherein R is a linear or branched chain hydrocarbyl group, more preferably an alkyl group as defined above, such as a linear or branched chain alkyl group. There may be multiple R groups attached to the benzene ring. The carboxylate group and hydroxyl group are conjugated to the aromatic ring, and this system has a negative (anionic) charge. The carboxylate group can be located in the ortho, meta, or para position relative to the hydroxyl group; the ortho position is preferred. The R group can be located in the ortho, meta, or para position relative to the hydroxyl group.

[0032] In a second anion embodiment, the one or more anions (ii) of the ionic liquid are most preferably one or more alkyl-substituted salicylate anions, wherein the alkyl substituent(s) of each anion are each independently selected from alkyl groups containing 12 to 24 carbon atoms; more preferably, dodecyl, tetradecyl, hexadecyl, and octadecyl. Such hydroxybenzoates and salicylates are typically prepared via the carboxylation of phenoxides by the Kolbe-Schmitt method, and are generally obtained in admixture with uncarboxylated phenol (usually in a dilute solution). In both the first and second preferred embodiments of anion (ii), each anion (ii) preferably does not contain nitrogen. The ionic liquid preferably contains one or more cations (i) and one or more anions (ii) derived from the above embodiments. In particular, the ionic liquid may preferably be composed of a combination of the cation (i) of the first embodiment and the anion (ii) of the carboxylate salt of either the first or second embodiment, or a mixture thereof. More preferably, the ionic liquid contains a combination of the cation (i) of the second embodiment and the anion (ii) of the carboxylate salt of either the first or second embodiment, or a mixture thereof.

[0033] Most preferably, the ionic liquid comprises a combination of the cation (i) of the second embodiment and the anion (ii) of the second embodiment that is a carboxylate. Such ionic liquids have a particularly high affinity for nitrogen dioxide and are particularly advantageous when formulated in accordance with various aspects of the present invention. Most preferably, in this combination, each of the cations (i) and anions (ii) is nitrogen-free. In particular, ionic liquids in which each cation (i) is nitrogen-free and comprises a tetrahydrocarbyl-substituted central atom or ring system bearing a cationic charge, and each anion (ii) comprises an aromatic ring bearing a carboxylate group, an additional heteroatom-containing functional group, and an additional hydrocarbyl substituent, as described hereinabove, are preferred. The preferred examples described herein for each of such cations (i) and anions (ii) are particularly useful in combination. Anion (ii) in which the heteroatom(s) in both functional groups consist of oxygen atoms is more preferred. Most preferably, these functional groups are located on adjacent ring carbon atoms in an "ortho" configuration relative to each other on the aromatic ring.

[0034] In all preferred ionic liquids, particularly those in the preceding three paragraphs, each cation (i) is most preferably an alkyl-substituted phosphonium cation, ideally a tetraalkyl-substituted phosphonium cation as described herein above, with the trihexyltetradecylphosphonium cation (P66614 cation) being most preferred. Ionic liquids of all aspects of the present invention may be prepared by synthetic routes known in the art, selected by those skilled in the art according to conventional synthetic criteria for suitability for the desired cation-anion combination. Thus, in the ionic liquid containing cation (i) of the first embodiment, this cation can be formed by alkylation or arylation, preferably alkylation, of the corresponding amine or nitrogen-containing ring compound using a nucleophilic substitution reaction with an alkylating or arylating agent, which may be, for example, an alkyl or aryl halide, preferably an alkyl halide. The resulting cation-halide complex can then be mixed with a desired stoichiometric amount of a metal salt of the desired anion (ii), typically in a dry organic solvent. The organic solvent is selected to solubilize the desired ionic liquid but precipitate the metal halide formed after anion exchange. An anion exchange resin can also be employed to facilitate the exchange reaction. In the ionic liquid containing cation (i) of the second embodiment, the liquid can similarly be formed from a cation-halide complex of the desired cation (ii), e.g., a preferred phosphonium cation, and the liquid then subjected to anion exchange with the desired anion precursor in a suitable solvent. An anion exchange resin may again be employed to facilitate the exchange. The solvent is then removed and the ionic liquid recovered. Examples of methods for synthesizing ionic liquids are described in US 2008 / 0251759 and in the working examples later in this specification, and the individual cations and anions, or their precursors, are available as commercial products in the chemical industry.

[0035] Without being bound by any particular theory, applicants believe that the particular benefit of the combination of ionic liquids as defined in the present invention with cleaning agents in deactivating the decomposition action of nitrogen dioxide arises from the composition and elucidated mechanism of action of the ionic liquids, which is enhanced or facilitated by the cleaning agents such that the efficacy of the ionic liquids is increased. First, the anion (ii) of the ion pair of the ionic liquid can interact with nitrogen dioxide molecules and effectively remove them from the reaction cycle within the hydrocarbon liquid, thereby inhibiting the initial deprotonation of hydrocarbon components in the bulk liquid, as well as the nitrification reaction sequence and the formation of nitrate esters, slowing the decomposition of the bulk liquid over time. We speculate that nitric acid, formed in situ from the oxidation of a portion of the bound nitrogen dioxide, is then trapped by the associated cations in the ionic liquid. This nitric acid loses its acidic proton to a negatively charged anion-nitrogen dioxide complex, forming an ion pair containing the ionic liquid cation and the nitrate anion, followed by the formation of a stable complex between the protonated anion and the remaining bound nitrogen dioxide. This sequence also effectively removes nitric acid from the reactive circulation within the hydrocarbon liquid. As a result, acid buildup in the hydrocarbon liquid over time is also slowed, and the ionic liquid helps contain acid-mediated oxidation and acid attack of the hydrocarbon liquid and the underlying mechanical equipment. In this manner, the cations and anions of the ionic liquid act in combination to inhibit decomposition of the hydrocarbon liquid as a result of nitrogen dioxide contamination, thereby extending its operational life.

[0036] The observable benefit resulting from the co-presence of the detergent is due to the detergent's ability to act as a proton transfer agent during the formation of the ion pair between the ionic liquid cation and the nitrate anion, thereby promoting the formation of further complexes between the protonated anion and the remaining bound nitrogen dioxide. In this way, the detergent cooperates with the ionic liquid to remove nitrogen dioxide from the reaction circulation within the hydrocarbon liquid, significantly inhibiting nitrification during operation.

[0037] Detergents incorporated in all aspects of the present invention The detergent additive comprises, as the active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts, with the remainder of the detergent composition suitably being a solvent or carrier fluid, optionally containing minor amounts of adjunct materials such as compatibilizers or antifoam agents. Metal-containing (or "ash-forming") detergents generally comprise a polar head with a long hydrophobic tail. The polar head comprises a metal salt of an acidic organic compound. The salt may contain a substantially stoichiometric amount of metal, in which case the salt is typically described as a normal or neutral salt, and its total base number, or TBN (determinable according to ASTM standard (ASTM) D2896), is from 0 to less than 150, e.g., from 0 to about 80 or 100. Large amounts of metal base may be incorporated by reacting an excess of a metal compound (e.g., oxide or hydroxide) with an acid gas (e.g., carbon dioxide). The resulting overbased detergent comprises a neutralized detergent as the outer layer of a metal base (e.g., carbonate) micelle. Such overbased detergents have a TBN (mg KOH / g) of 150 or greater, and preferably have a TBN of at least about 200, e.g., from about 200 to about 500; preferably at least about 250, e.g., from about 250 to about 500; more preferably at least about 300, e.g., from about 300 to about 450.

[0038] In all aspects of the present invention, the detergent active ingredient is preferably one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted aromatic acids or phenols, or includes such metal salts. Preferred active ingredients that may be incorporated in all aspects of the present invention include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphates, salicylates, and naphthenates, as well as other oil-soluble carboxylates of metals, particularly alkali or alkaline earth metals such as barium, sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, and both may be present in detergents used in lubricants, as well as in mixtures of calcium and / or magnesium with sodium. Combinations of detergents, whether overbased, neutral, or both, may also be used. More preferably, the detergent active ingredient is or includes one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted benzenesulfonic acids. Such sulfonic acids are typically obtained by sulfonating alkyl-substituted aromatic hydrocarbons, such as those obtained from petroleum fractionation, or by alkylating aromatic hydrocarbons. Examples include those obtained by alkylating benzene, toluene, xylene, naphthalene, diphenyl, or their halogen derivatives, such as chlorobenzene, chlorotoluene, and chloronaphthalene. The alkylation may be carried out in the presence of a catalyst using an alkylating agent having from about 3 to more than 70 carbon atoms. The alkaryl sulfonate typically has from about 9 to about 80 or more carbon atoms, preferably from about 16 to about 60, per alkyl-substituted aromatic moiety.

[0039] The oil-soluble sulfonates or alkaryl sulfonic acids may be neutralized with metal oxides, hydroxides, alkoxides, carbonates, carboxylates, sulfides, hydrosulfides, nitrates, borates, and ethers. The amount of metal compound is selected based on the desired TBN of the final product, but is typically in the range of about 100 to 220% by weight (preferably at least 125% by weight) of the stoichiometrically required amount. The detergents may also preferably comprise, or consist of, as the active ingredient, one or more metal salts of hydrocarbyl-substituted or sulfurized phenols prepared by reaction with suitable metal compounds such as oxides or hydroxides, and the neutral or overbased products may be obtained by methods well known in the art. Sulfurized phenols may be prepared by reacting phenol with sulfur or a sulfur-containing compound such as hydrogen sulfide, sulfur monohalide, or sulfur dihalide to form a product that is generally a mixture of compounds linking two or more phenols with a sulfur-containing bridge. Most preferably, the detergent active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted carboxylic acids, more preferably one or more neutral or overbased metal salts of one or more hydroxybenzoic acids.

[0040] Such carboxylate detergents can be prepared by reacting an aromatic carboxylic acid with a suitable metal compound, such as an oxide or hydroxide, and neutral or overbased products may be obtained by methods well known in the art. The aromatic moiety of the aromatic carboxylic acid can contain heteroatoms, such as nitrogen and oxygen. Preferably, the moiety contains only carbon atoms; more preferably, the moiety contains six or more carbon atoms; for example, benzene is a preferred moiety. The aromatic carboxylic acid may contain one or more aromatic moieties, such as one or more benzene rings, fused or linked via alkylene bridges. The carboxyl moiety may be directly or indirectly attached to the aromatic moiety. Preferably, the carboxylic acid group is attached directly to a carbon atom on the aromatic moiety, such as a carbon atom on a benzene ring. More preferably, the aromatic moiety also contains a second functional group, such as a hydroxy group or a sulfonate group, which may be attached directly or indirectly to a carbon atom on the aromatic moiety. Preferred examples of aromatic carboxylic acids include salicylic acid and its sulfurized derivatives, such as hydrocarbyl-substituted salicylic acid and its derivatives. Methods for sulfurizing, for example, hydrocarbyl-substituted salicylic acid are known to those skilled in the art. Salicylic acid is typically prepared by carboxylation of phenoxides, for example, using the Kolbe-Schmitt method, and is generally obtained in admixture with uncarboxylated phenol, usually in a diluent.

[0041] Preferred substituents in oil-soluble salicylic acids are alkyl substituents. In alkyl-substituted salicylic acids, the number of carbon atoms in the alkyl group is advantageously 5 to 100, preferably 9 to 30, and especially 14 to 20. When there are multiple alkyl groups, the average number of carbon atoms in all the alkyl groups is preferably at least 9 to ensure sufficient oil solubility. In all aspects of the invention, it is particularly preferred that the detergent active ingredient is one or more alkaline earth metal salts of alkyl-substituted salicylic acids, most preferably one or more magnesium salts of alkyl-substituted salicylic acids. In both such embodiments, it is most preferred that the alkyl substituent(s) of each salicylate comprising the detergent active ingredient are each independently selected from alkyl groups containing from 9 to 30 carbon atoms, especially from 14 to 20 carbon atoms.

[0042] In the practice of this invention, detergents containing magnesium salts are preferred. In all aspects of this invention, the magnesium detergent may be the sole metal-containing detergent, in which case 100% of the metal introduced into the lubricating oil composition by the detergent is magnesium. When overbased or neutral detergents based on metals other than magnesium are employed, preferably at least about 30 wt. %, more preferably at least about 40 wt. %, and especially at least about 50 wt. % of the total metal introduced into the lubricating oil composition by the detergent is magnesium. Detergents generally useful in formulating lubricating oil compositions also include "hybrid" detergents formed using mixed surfactant systems, such as phenate / salicylate, sulfonate / phenate, sulfonate / salicylate, sulfonate / phenate / salicylate, as described, for example, in U.S. Pat. Nos. 6,153,565; 6,281,179; 6,429,178, and 6,429,178.

[0043] Hydrocarbon liquids formulated according to the second, third, fourth, and fifth aspects of the present invention The hydrocarbon liquids used as bulk operating liquids in these aspects of the invention may be obtained from petroleum or synthetic sources, or from biomaterial processing. When the hydrocarbon fluid is a petroleum oil, particularly a lubricating oil, the viscosity of such fluids ranges from light distillate mineral oils to heavy lubricating oils such as gasoline engine oils, mineral lubricating oils, and heavy-duty diesel oils. Generally, the kinematic viscosity of fluids is about 2 mm, measured at 100°C (ASTM D445-19a). 2 / sec (centistokes) ~ approx. 40 mm 2 / sec, especially around 3mm 2 / sec ~ approx. 20mm 2 / sec, most preferably about 9mm 2 / sec ~ approx. 17mm 2 / second range. Suitable oils, particularly lubricating oils, include natural oils such as animal and vegetable oils (e.g., castor oil, lard oil); liquid petroleum oils; and hydrotreated, solvent-treated, or acid-treated mineral oils of the paraffinic, naphthenic, and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale also serve as useful bulk oils.

[0044] Synthetic oils, particularly synthetic lubricating oils, include hydrocarbon oils and halo-substituted hydrocarbon oils that retain hydrocarbon character, such as polymerized and copolymerized olefins (e.g., ethylene-propylene copolymers, polybutylene homopolymers and copolymers, polypropylene homopolymers and copolymers, propylene-isobutylene copolymers, chlorinated polybutylene, poly(1-hexene), poly(1-octene), poly-n-decene (e.g., decene homopolymers or copolymers of decene with one or more C8-C20 alkenes other than decene, such as octene, nonene, undecene, dodecene, tetradecene, etc.)); alkylbenzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di(2-ethylhexyl)benzene); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides, and their derivatives, analogs, and homologs. Also useful are synthetic oils obtained from Fischer-Tropsch synthesized hydrocarbons in a gas-to-liquid process, commonly referred to as gas-to-liquids, or "GTL" base oils. Esters are useful as synthetic oils having hydrocarbon character, such as those formed from C5-C12 monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tripentaerythritol.

[0045] When the hydrocarbon fluid is a lubricating oil, it may comprise a Group I, Group II, Group III, Group IV, or Group V base stock, or a blend of the foregoing base stocks. Preferably, the lubricating oil is a Group II, Group III, Group IV, or Group V base stock, or a mixture thereof, such as a mixture of a Group I base stock with one or more Group II, Group III, Group IV, or Group V base stocks. Definitions of these base stocks and base oils are found in "Engine Oil Licensing and Certification System ("ELOCS")," published by the American Petroleum Institute (API), Industry Services Division, December 1996, 14th Edition, Supplement 1, December 1998. Preferably, the base stock or base stock blend has a saturate content of at least 65%, more preferably at least 75%, e.g., at least 85%. Preferably, the base stock or base stock blend is a Group III or higher base stock or base stock blend, or a blend of a Group II base stock and a Group III or higher base stock or base stock blend. Most preferably, the base stock or base stock blend has a saturate content of greater than 90%. Preferably, the oil or oil blend has a sulfur content of less than 1%, preferably less than 0.6%, most preferably less than 0.4%, e.g., less than 0.3%, by weight (measured as set forth in API EOLCS). Group III base stocks have been found to have increased wear credit compared to Group I base stocks, and therefore, in a preferred embodiment, at least 30%, preferably at least 50%, more preferably at least 80%, by weight of the lubricating oil is Group III base stock. Preferably, the volatility of the lubricating oil or lubricating oil blend is 30% by weight or less, such as about 25% by weight or less, preferably 20% by weight or less, more preferably 15% by weight or less, and most preferably 13% by weight or less, as measured by the Noack test (ASTM D5800). Preferably, the viscosity index (VI) of the oil or oil blend is at least 85, preferably at least 100, and most preferably about 105 to 140 (ASTM D2270).

[0046] Additive composition according to the first aspect of the present invention A first aspect of the present invention is an additive composition for hydrocarbon fluids, the additive composition comprising an ionic liquid, a detergent, and a carrier fluid, optionally with further additives. For easier mixing or blending, it may be desirable to prepare the additive composition as a concentrate comprising the ionic liquid and detergent in a carrier fluid (a diluent or solvent that is mutually compatible with both the ionic liquid and the hydrocarbon fluid), so that other additives can be simultaneously added to the concentrate, and thus to the hydrocarbon fluid, to form the hydrocarbon fluid composition (such a concentrate may be referred to as an additive package). The ionic liquid may be added to the additive concentrate before combining the concentrate with the hydrocarbon fluid, or to the combination of the additive concentrate and the hydrocarbon fluid. The ionic liquid may be added to the additive package before combining the package with the hydrocarbon fluid, or to the combination of the additive package and the hydrocarbon fluid.

[0047] When an additive concentrate is used, its content may be 5 to 25% by weight, preferably 5 to 22% by weight, typically 10 to 20% by weight, based on the active ingredient, with the remainder of the concentrate being the solvent or diluent. As a convenient method of simultaneously incorporating multiple additives into a hydrocarbon fluid, the additive composition (preferably in the form of a concentrate) may also contain additional additives that can vary in properties and applications depending on the needs of the target operating fluid. When the hydrocarbon fluid is a lubricating oil or power transmission oil, particularly an engine lubricant, various additional additives may be incorporated to enhance other properties of the fluid. The additional additives may include one or more dispersants; phosphorus-containing compounds; non-metal-containing detergents; anti-wear agents; friction modifiers, viscosity modifiers; antioxidants; and other co-additives, although these additives are different from the essential ionic liquids and detergents described herein above. These additives are described in more detail below. Dispersants are additives whose primary function is to hold oil-insoluble contaminants in suspension, thereby passivating the contaminants and reducing surface deposition. For example, dispersants maintain oil-insoluble materials in suspension that result from oxidation during use, preventing the solids from flocculating, settling, or depositing on machinery parts.

[0048] Dispersants in the present invention are "ashless"—non-metallic organic materials that produce little or no ash upon combustion, as opposed to metal-containing, ash-forming materials. Dispersants comprise long hydrocarbon chains with polar ends, the polarity preferably resulting from the inclusion of oxygen, phosphorus, or nitrogen atoms. The hydrocarbon is an oleophilic group that confers oil solubility and has, for example, 40 to 500 carbon atoms, e.g., 60 to 250 carbon atoms. Thus, ashless dispersants may comprise an oil-soluble polymeric backbone. The number average molecular weight (Mn) of the hydrocarbon portion of the dispersant may be 800 to 5000 g / mol, e.g., 900 to 3000 g / mol. A preferred type of olefin polymer includes polybutene, specifically polyisobutene (PIB), or poly-n-butene, which may be prepared, for example, by polymerization of a C4 refinery stream.

[0049] Dispersants include, for example, derivatives of long-chain hydrocarbon-substituted carboxylic acids, such as derivatives of high molecular weight hydrocarbyl-substituted succinic acids. Typically, a hydrocarbon polymer material such as polyisobutylene is reacted with an acylating group (e.g., maleic acid or anhydride) to form the hydrocarbon-substituted succinic acid (succinate). A notable group of dispersants comprises, for example, hydrocarbon-substituted succinimides formed by reacting the above acids (or derivatives) with nitrogen-containing compounds, preferably polyalkylenepolyamines, such as polyethylenepolyamines. Particularly preferred are reaction products of polyalkylenepolyamines with alkenylsuccinic anhydrides, as described in U.S. Patents 3,202,678; 3,154,560; 3,172,892; 3,024,195; 3,024,237; 3,219,666; and 3,216,936, which may be post-treated to improve their properties, for example, by boration (as described in U.S. Patents 3,087,936 and 3,254,025), fluorination, or oxylation. For example, boration may be carried out by treating an acyl nitrogen-containing dispersant with a boron compound selected from boron oxide, boron halides, boric acid, and esters of boric acid. Preferably, the dispersant, if present, is a medium functionality polyisobutene-derived succinimide dispersant having a number average molecular weight in the range of 800 to 5000 g / mol, for example 1000 to 3000 g / mol, preferably 1500 to 2500 g / mol. Preferably, the succinimide is derived from a highly reactive polyisobutene.

[0050] Another example of a type of dispersant that may be used is a linked aromatic compound such as those described in EP-A-090 642. Combinations of borated and non-borated succinimides are useful herein. Combinations of one or more (e.g., two or more) high Mn (Mn ≥ 1500 g / mol, e.g., ≥ 2000 g / mol) succinimides with one or more (e.g., two or more) low Mn (Mn < 1500 g / mol, e.g., < 1200 g / mol) succinimides are useful herein, which combinations may optionally contain one, two, three, or more borated succinimides.

[0051] Suitable phosphorus-containing compounds include dihydrocarbyl dithiophosphate metal salts, which are frequently used as antiwear and antioxidant agents. The metal is preferably zinc, but may also be an alkali or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel, or copper. Zinc salts are most commonly used in lubricating oils in amounts of 0.1 to 10 mass %, preferably 0.2 to 2 mass %, based on the total mass of the lubricating oil composition. Zinc salts may be prepared according to known techniques by first reacting P2S5 with, typically, one or more alcohols or phenols to form a dihydrocarbyl dithiophosphate (DDPA), and then neutralizing the DDPA with a zinc compound. For example, a dithiophosphate may be prepared by reacting a mixture of primary and secondary alcohols. Alternatively, multiple dithiophosphates can be prepared where the hydrocarbyl groups on one are entirely secondary in character and the hydrocarbyl groups on the other are entirely primary in character. Any basic or neutral zinc compound can be used to prepare the zinc salt, although oxides, hydroxides, and carbonates are most commonly used. Commercially available additives often contain excess zinc due to the use of excess basic zinc compounds in the neutralization reaction.

[0052] Preferred zinc dihydrocarbyl dithiophosphates are oil-soluble salts of dihydrocarbyl dithiophosphates and may be represented by the formula: [ka] In the formula, R and R' may be the same or different hydrocarbyl radicals having 1 to 18 carbon atoms, preferably 2 to 12 carbon atoms, including alkyl, alkenyl, aryl, arylalkyl, alkaryl, and alicyclic radicals. In this context, it is particularly preferred that the R and R' groups be alkyl groups having 2 to 8 carbon atoms. Thus, the radicals may be, for example, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, or butenyl. To achieve oil solubility, the total number of carbon atoms (i.e., R and R') in the dithiophosphoric acid is generally 5 or greater. Thus, the zinc dihydrocarbyl dithiophosphate (ZDDP) can include a zinc dialkyldithiophosphate. The phosphorus content of the additive concentrates of the present invention for lubricants may be 100 to 1500 ppm, e.g., 200 to 1200 ppm, e.g., 600 to 900 ppm, e.g., about 0.08 wt. % (800 ppm) or less, according to ASTM D5185. Preferably, in the practice of the present invention, ZDDP is used in an amount close to or equal to the maximum allowable amount, preferably an amount such that the phosphorus content is within the 100 ppm maximum allowable amount of phosphorus. Accordingly, the resulting lubricating oil composition preferably contains ZDDP or other zinc-phosphorus compound in an amount such that the phosphorus content is 0.01 to 0.08 wt. %, e.g., 0.04 to 0.08 wt. %, preferably 0.05 to 0.08 wt. %, based on the total weight of the lubricating oil composition.

[0053] Additional additives may be incorporated into the additive concentrate of the present invention to enable it to meet specific performance requirements. Examples of such additives that may be included in the lubricating oil composition of the present invention include friction modifiers, viscosity modifiers, metal rust inhibitors, viscosity index improvers, corrosion inhibitors, antioxidants, antifoam agents, antiwear agents, and pour point depressants. The lubricating oil composition may also contain friction modifiers (and, in engine lubricants, fuel economy agents) that are compatible with the other components of the hydrocarbon fluid. Examples of such materials include glyceryl monoesters of higher fatty acids, such as glyceryl monooleate; esters of long-chain polycarboxylic acids with diols, such as butanediol esters of dimerized unsaturated fatty acids; and alkoxylated alkyl-substituted monoamines, diamines, and alkyl ether amines, such as ethoxylated tallow amine and ethoxylated tallow ether amine. Other known friction modifiers include oil-soluble organo-molybdenum compounds. These organo-molybdenum friction modifiers provide antioxidant and anti-wear credits to lubricating oil compositions. Examples of such oil-soluble organo-molybdenum compounds include dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates, sulfides, and the like, and mixtures thereof. Molybdenum dithiocarbamates, dialkyldithiophosphates, alkylxanthates, and alkylthioxanthates are particularly preferred.

[0054] The molybdenum compound may also be an acidic molybdenum compound. These compounds react with basic nitrogen compounds, typically hexavalent, as determined by ASTM Test D-664 or D-2896 titration procedures. Molybdenum compounds include molybdic acid, ammonium molybdate, sodium molybdate, potassium molybdate, and other alkali metal molybdates, as well as other molybdenum salts such as sodium hydrogen molybdate, MoOCl4, MoO2Br2, Mo2O3Cl6, molybdenum trioxide, or similar acidic molybdenum compounds. Among the molybdenum compounds useful in the compositions of the present invention are organomolybdenum compounds represented by the formula: Mo(R”OCS2)4, and Mo(R”SCS2)4 In the formula, R" is an organic group selected from the group consisting of alkyl, aryl, aralkyl, and alkoxyalkyl, generally having 1 to 30 carbon atoms, preferably 2 to 12 carbon atoms, with alkyl having 2 to 12 carbon atoms being most preferred. Dialkyldithiocarbamates of molybdenum are particularly preferred.

[0055] Another group of organo-molybdenum compounds useful as additional additives in the present invention includes trinuclear molybdenum compounds, particularly those of the formula Mo3S k A n D z and mixtures thereof, wherein A is an independently selected ligand having organic groups with a sufficient number of carbon atoms to render the compound soluble or dispersible in oil, n is 1 to 4, k is in the range of 4 to 7, D is selected from the group of neutral electron donor compounds such as water, amines, alcohols, phosphines, and ethers, and z is in the range of 0 to 5, including non-stoichiometric values. It is desirable to have at least 21 carbon atoms, e.g., at least 25, at least 30, or at least 35 carbon atoms, among all of the ligand organic groups. When the additive is used in a hydrocarbon fluid as a lubricating oil, the additive preferably contains at least 10 ppm, at least 30 ppm, at least 40 ppm, more preferably at least 50 ppm of molybdenum. Suitably, the molybdenum content of such lubricating oil compositions is 1000 ppm or less, 750 ppm or less, or 500 ppm or less. Preferably, the molybdenum content of the lubricating oil compositions useful in the present invention is 10 to 1000 ppm, e.g., 30 to 750 ppm, or 40 to 500 ppm (measured as molybdenum atoms).

[0056] The viscosity index of hydrocarbon fluids, particularly lubricating oils, may be increased or improved by incorporating into the additive composition certain polymeric materials that function as viscosity modifiers (VM) or viscosity index improvers (VII). Generally, polymeric materials useful as viscosity modifiers have a number average molecular weight (Mn) of 5,000 to 250,000, preferably 15,000 to 200,000, and more preferably 20,000 to 150,000. These viscosity modifiers can be grafted with grafting materials, such as maleic anhydride. The grafting materials can be reacted with, for example, amines, amides, nitrogen-containing heterocycles, or alcohols to form multifunctional viscosity modifiers (dispersant-viscosity modifiers). Polymers prepared using diolefins will contain ethylenic unsaturation, and it is preferable to hydrogenate such polymers. If the polymer is hydrogenated, the hydrogenation may be carried out by any technique known in the prior art. For example, hydrogenation may be carried out to convert (saturate) both the ethylenic and aromatic unsaturations using methods such as those taught in U.S. Pat. Nos. 3,113,986 and 3,700,633. Alternatively, hydrogenation may be carried out selectively to convert most of the ethylenic unsaturation without converting most or all of the aromatic unsaturation, as taught in U.S. Pat. Nos. 3,634,595; 3,670,054; 3,700,633, and Reissue No. 27,145. Any of these methods can also be used to hydrogenate polymers containing only ethylenic unsaturation and no aromatic unsaturation.

[0057] Pour point depressants (PPDs) lower the minimum temperature at which the bulk fluid will flow and may be present in additives, particularly lubricating oils. PPDs can be grafted with grafting materials, such as maleic anhydride. The grafting materials can be reacted with, for example, amines, amides, nitrogen-containing heterocycles, or alcohols to form multifunctional additives. In the present invention, it may be advantageous to include a co-additive that maintains the stability of the blend's viscosity. Thus, while polar group-containing additives achieve a suitably low viscosity at the pre-blending stage, it has been observed that some compositions experience viscosity buildup upon prolonged storage. Additives effective in controlling this viscosity buildup include long-chain hydrocarbons functionalized by reaction with mono- or dicarboxylic acids or anhydrides used in the preparation of ashless dispersants, as disclosed hereinabove. When the additive of the first embodiment contains one or more of the additional additives described above in addition to the ionic liquid, each additional additive is typically blended into the bulk liquid in an amount such that the additive provides the desired function.

[0058] Hydrocarbon liquid composition according to the second aspect of the present invention A second aspect of the present invention is a hydrocarbon liquid composition comprising a predominant amount of a hydrocarbon liquid and minor amounts of an ionic liquid and a detergent additive. The ionic liquid comprises: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as the active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts. Such hydrocarbon liquid compositions are preferably formed from the ionic liquid, detergent and hydrocarbon liquid described herein and are obtained or obtainable by the method or use of the third, fourth or fifth aspects of the invention below. The hydrocarbon liquid composition may further contain additional additives as described in the first aspect of the invention.

[0059] Representative effective amounts of such additional additives for use in hydrocarbon fluids that are crankcase lubricants are listed in the table below. All values ​​listed (except for the detergent values, since the detergents are used in the form of colloidal dispersions in the oil) are listed as active ingredients (AI) expressed as mass percent. These amounts of additional additives are used in combination with the ionic liquids and detergents described above in this specification. [Table 1]

[0060] The ionic liquid, detergent, and other desired additives may be added to the hydrocarbon liquid by physical mixing or blending techniques known in the art. Although not required, to facilitate easier mixing or blending, it may be desirable to prepare one or more additive compositions of the first aspect comprising the ionic liquid and detergent in a carrier liquid (a diluent or solvent that is mutually compatible with both the ionic liquid and the hydrocarbon liquid), ideally in the form of a concentrate (such a concentrate may be referred to as an additive package), so that other additives can be simultaneously added to the concentrate, and thus to the hydrocarbon liquid, to form the composition of the second aspect.

[0061] The method of the third aspect of the invention A third aspect of the present invention is a method for limiting chemical decomposition of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180°C, comprising the combination of an ionic liquid and a detergent as described above. The decomposition is initiated by nitration of the liquid resulting from nitrogen dioxide contamination during operation. The method comprises: preparing or obtaining a freshly prepared hydrocarbon liquid suitable for operation at a bulk liquid temperature of 60 to 180°C and free of aging components and nitrogen dioxide contamination; and adding an ionic liquid and a detergent additive as defined above to the hydrocarbon liquid prior to operation at a bulk liquid temperature of from 60 to 180°C, wherein the ionic liquid and detergent additive components are added in amounts cooperatively effective to inhibit nitration of the hydrocarbon liquid during and after operation at a bulk liquid temperature of from 60 to 180°C in the presence of nitrogen dioxide contamination; and subjecting said hydrocarbon liquid to operation, whereby the ionic liquid and detergent additives limit chemical decomposition of the resulting liquid. Includes:

[0062] In this method, the combined effectiveness of the ionic liquid and detergent in inhibiting the nitrogen dioxide-initiated nitrification reaction on hydrocarbon compounds at elevated temperatures delays the onset of bulk liquid decomposition via this chemical pathway and extends its operational life. The ionic liquid initially acts via inhibition of proton abstraction by nitrogen dioxide, which initiates bulk liquid nitrification, delaying the initial formation of free radicals that lead to other chemical reactions further down the pathway, delaying the onset of significant decomposition. The ionic liquid and detergent further act later in the pathway by inhibiting the formation of hydrocarbon-based nitrate esters from the subsequent reaction of nitrogen dioxide with RO radicals, reducing the accumulation of these reactive compounds in the bulk liquid. As a result, the bulk liquid is exposed to low concentrations of emitted RO radicals at elevated temperatures, particularly under operating temperature increases (continuous or cyclic) above 110°C, where the dissociation rate of these nitrate esters increases significantly, enhancing severe bulk liquid decomposition.

[0063] The amounts of ionic liquid and detergent active ingredients effective to cooperatively inhibit nitrification in the method of the present invention can be determined by routine testing under conditions that replicate or simulate nitrogen dioxide contamination at the high operating temperatures experienced in the system of interest. In a preferred embodiment of the method, the chemical decomposition inhibited by the combination of ionic liquid and detergent is due to the decomposition of hydrocarbon nitrates formed during operation by nitration of hydrocarbon liquors with nitrogen dioxide at bulk liquid temperatures between 60 and 180°C, and the ionic liquid and detergent active ingredients are added in amounts determined to inhibit the formation of hydrocarbon nitrates during operation, thus directly inhibiting the buildup of reservoirs of reactive hydrocarbon nitrates at high operating temperatures and better limiting their decomposition. In a more preferred embodiment of the method, the chemical decomposition inhibited by the ionic liquid / detergent combination results from the decomposition of hydrocarbon nitrates by subjecting the hydrocarbon liquid to bulk liquid temperatures of 110-160°C periodically or continuously during operation, and the ionic liquid and detergent active ingredients are added in amounts determined to inhibit the formation of hydrocarbon nitrates during operation, thus directly inhibiting the more rapid and severe decomposition that occurs during operation at higher temperatures.

[0064] In these embodiments of the present invention, the level of nitrate ester formation in the bulk liquid can be determined spectroscopically by observing the increase over time in the infrared peak height associated with the nitrate ester in the bulk liquid under suitable test conditions. This spectroscopic approach allows the amount of ionic liquid and detergent required to inhibit nitrate ester formation in the bulk liquid to be determined. Inhibition of hydrocarbon nitrate ester formation during operation is determined by observing the decrease in the nitrate ester peak height in the bulk liquid in the combined presence of the ionic liquid and detergent active ingredient. This peak height is measured by infrared spectroscopy under similar conditions of operation and nitrogen dioxide contamination according to German Industrial Standard (DIN) 51 453 or ASTM D8048-20 (in the event of a conflict between DIN 51 453 and ASTM D8048-20, DIN 51 453 shall prevail). According to the DIN method, the nitrate ester peak height at 1630 cm -1 The height of the single infrared absorption frequency is 1615 cm -1 and 1645cm -1 The peak height is measured above a linear baseline defined by the absorbance at 1950 cm. The higher the peak height, the more nitrate esters there are in the bulk fluid. By measuring a series of samples taken over time, it is also possible to track the change in peak height as the nitrate ester level in the operating fluid changes over time. According to the ASTM D8048-20 standard test method, the oxidation and nitration peak heights are measured by first subtracting the infrared spectrum of a new fluid. The baseline is measured at 1950 cm. -1 ~1850cm -1 The highest peak is 1740 cm for oxidation. -1 ~1700cm -1range, and nitrification is 1640 cm -1 ~1620cm -1 is.

[0065] The amount of reduction or limitation of nitrate ester formation in a lubricating oil composition is determined by observing that the nitrate ester peak height in the presence of a lubricating oil composition containing an ionic liquid is lower (at least 10%, such as at least 20%, such as at least 30%, such as at least 40%, such as at least 50%, such as 100% lower) (compared to the nitrate ester peak of the same lubricating oil composition in which the ionic liquid is replaced with an ionic liquid having the same cation but the same proportion of hexanoate as the anion), as measured by infrared spectroscopy under similar conditions of operation and nitrogen dioxide contamination according to DIN 51 453 or ASTM D8048-20, except that in the event of a conflict between DIN 51 453 and ASTM D8048-20, DIN 51 453 shall be followed. However, under normal circumstances, the amount of ionic liquid added to inhibit nitration of the hydrocarbon liquid during subsequent operation at bulk liquid temperatures of 60°C or higher, e.g., 110°C or higher, e.g., 60-180°C (e.g., 60-180°C, e.g., 60-160°C, e.g., 110-160°C, e.g., 130-160°C) in the presence of nitrogen dioxide contamination, is 0.1-5.0 wt% per mass of hydrocarbon liquid; preferably, 0.5-4.0 wt% per mass of hydrocarbon liquid. More preferably, the ionic liquid is added in an amount ranging from 1.0-3.5 wt% per mass of hydrocarbon liquid; most preferably, 1.0-3.0 wt% per mass of hydrocarbon liquid.

[0066] Under normal circumstances, the amount of detergent added to inhibit nitration of the hydrocarbon liquid during operation at bulk liquid temperatures of 60°C to 180°C in the presence of nitrogen dioxide contamination will then be in the range of 0.2 to 5.0 wt.% active ingredient per mass of hydrocarbon liquid; preferably, 0.5 to 4.0 wt.% active ingredient per mass of hydrocarbon liquid. Most preferably, the detergent is added in an amount in the range of 1.0 to 3.0 wt.% active ingredient per mass of hydrocarbon liquid; most preferably, 1.5 to 2.5 wt.% active ingredient per mass of hydrocarbon liquid. The hydrocarbon fluids formulated by the methods of the present invention are suitable for operation at bulk fluid temperatures of 60°C or higher, e.g., 110°C or higher, e.g., 60-180°C (e.g., 60-180°C, e.g., 60-160°C, e.g., 110-160°C, e.g., 130-160°C), and are free of aging components and nitrogen dioxide contamination (or substantially free, e.g., less than 5 ppm aging components and less than 10 ppm nitrogen dioxide contamination) prior to operation. Such operating fluids are used in a variety of applications, including industrial and automotive oils, and power transmission fluids such as engine lubricants.

[0067] In this application, the hydrocarbon liquid is preferably a mechanical lubricant. More preferably, the hydrocarbon liquid is a crankcase lubricant for an internal combustion engine, which during operation is subject to nitrogen dioxide contamination from exhaust gases, which are entrained in the lubricant by the gas blow-by effect in the crankcase and come into direct contact with the engine's cylinder walls. Most preferably, the crankcase lubricant is one that is periodically or continuously exposed to bulk liquid temperatures in the crankcase of 110-160°C. To be of benefit to this use, it is important that, prior to operation, the hydrocarbon liquid is initially free of nitrogen dioxide contamination and aged liquid components resulting from oxidative or other chemical breakdown during operation, so as not to introduce significant amounts of reactive species into the liquid that could lead to alternative or complementary decomposition pathways to nitrogen dioxide-initiated nitrification. Thus, preferably, the hydrocarbon liquid should be freshly prepared and not have been used in a previous operation; it should not be premixed or diluted with a portion of previously used or nitrogen dioxide-contaminated aged liquid prior to operation. Alternatively, prior to operation, the hydrocarbon liquid may initially be substantially free (10 ppm or less, e.g., 5 ppm or less, e.g., 0 ppm) of nitrogen dioxide contamination and also substantially free (10 ppm or less, e.g., 5 ppm or less, e.g., 0 ppm) of aged liquid components resulting from oxidative or other chemical breakdown during operation (or, for example, substantially free of aged components at less than 0.0001 wt % and substantially free of nitrogen dioxide contamination at less than 10 ppm).

[0068] It is also important to add the ionic liquid prior to the onset of operation and the resulting high temperatures and nitrogen dioxide pollution to maximize its nitrification-inhibiting effect and counteract the buildup of nitrogen dioxide concentrations in the bulk liquid. In the present method, the ionic liquid and detergent can be added to the hydrocarbon fluid by physical mixing or blending techniques known in the art. Although not required, to facilitate easier mixing or blending, it may be desirable to prepare one or more additive compositions of the first aspect comprising the ionic liquid and detergent in a carrier fluid (a diluent or solvent that is mutually compatible with both the ionic liquid and the hydrocarbon fluid), so that other additives can be simultaneously added to a concentrate, and thus to the fluid, to form the lubricating oil composition (such a concentrate is sometimes referred to as an additive package). When an additive concentrate is used, its content may be 5 to 25% by weight of the ionic liquid, preferably 5 to 22% by weight, typically 10 to 20% by weight, with the remainder of the concentrate being solvent or diluent. The advantageous properties of this use in limiting chemical degradation by nitrification are demonstrated below in the inventive working examples.

[0069] Use of the fourth aspect of the invention A fourth aspect of the present invention provides the cooperative use of an ionic liquid and a detergent additive as described herein above to limit chemical decomposition of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180° C. The decomposition is initiated by nitration of the hydrocarbon liquid due to nitrogen dioxide contamination during operation, where the ionic liquid and detergent are added to a hydrocarbon liquid free of stale components and nitrogen dioxide contamination prior to operation, and the ionic liquid and detergent thereafter inhibit nitration of the hydrocarbon liquid during operation at bulk liquid temperatures between 60 and 180° C. in the presence of nitrogen dioxide contamination. A fourth aspect of the present invention involves the use of an ionic liquid and a detergent to inhibit nitration of a hydrocarbon liquid initiated by nitrogen dioxide contamination in operation at bulk liquid temperatures between 60 and 180° C. In this use, the ionic liquid and detergent function as described herein above, cooperating to limit chemical decomposition of the bulk hydrocarbon liquid due to nitrogen dioxide contamination. Suitable and preferred ionic liquids, detergents and hydrocarbon liquids for this use aspect of the invention are those previously described herein. The amounts of ionic liquid and detergent that are cooperatively effective to inhibit nitrification in this use of the present invention can be determined by routine testing under conditions that replicate or simulate the nitrogen dioxide contamination at high operating temperatures experienced in the system of interest.

[0070] In a preferred embodiment of this use, the chemical decomposition inhibited by the ionic liquid and detergent is due to the decomposition of hydrocarbon nitrates formed during operation by nitration of hydrocarbon liquids with nitrogen dioxide at bulk liquid temperatures between 60 and 180°C, and the ionic liquid and detergent inhibit the formation of hydrocarbon nitrates during that operation, thus directly inhibiting the buildup of reactive hydrocarbon nitrate reservoirs at high operating temperatures and better limiting decomposition. In a more preferred embodiment of this application, the chemical decomposition inhibited by the ionic liquid and cleaning agent results from the decomposition of hydrocarbon nitrates caused by periodically or continuously subjecting the hydrocarbon liquid to bulk liquid temperatures of 110-160°C during operation, and the ionic liquid and cleaning agent inhibit the formation of hydrocarbon nitrates during operation, thus directly inhibiting the more rapid and severe decomposition that occurs during operation at high temperatures.

[0071] In these use embodiments of the present invention, the level of nitrate ester formation in the bulk liquid can be determined spectroscopically by observing the increase over time in the infrared peak height associated with the nitrate ester in the bulk liquid under suitable test conditions. This spectroscopic approach allows the effectiveness of the ionic liquid and detergent to be observed for inhibiting nitrate ester formation in the bulk liquid. Inhibition of hydrocarbon-based nitrate ester formation during operation is determined by observing a relatively low nitrate ester peak height in the bulk liquid in the combined presence of the ionic liquid and detergent. This peak height is measured by infrared spectroscopy in accordance with DIN 51 453 or ASTM D8048-20, compared to the nitrate ester peak observed with the ionic liquid or detergent active ingredient alone under similar conditions of operation and nitrogen dioxide contamination. According to this DIN method, the nitrate ester peak at 1630 cm -1 The height of the single infrared absorption frequency is 1615 cm -1 and 1645cm -1 The peak height is measured above a linear baseline defined by the absorbance at 1950 cm. The higher the peak height, the more nitrate esters there are in the bulk fluid. Measuring a series of samples taken over time also makes it possible to track changes in peak height as the nitrate ester level in the operating fluid changes over time. According to the ASTM D8048-20 standard test method, the oxidation and nitrification peak heights are measured by first subtracting the infrared spectrum of a new fluid. The baseline is measured at 1950 cm. -1 ~1850cm -1 The highest peak is at 1740 cm for oxidation. -1 ~1700cm -1 range, nitrification at 1640 cm -1 ~1620cm -1 The range is.

[0072] However, under normal circumstances, the amount of ionic liquid used to inhibit nitration of hydrocarbon liquids in the presence of nitrogen dioxide contamination and during operation at bulk liquid temperatures of 60-180°C is in the range of 0.1-5.0 wt% per mass of hydrocarbon liquid; preferably, 0.5-4.0 wt% per mass of hydrocarbon liquid. More preferably, the ionic liquid is used in an amount in the range of 1.0-3.5 wt% per mass of hydrocarbon liquid; most preferably, 1.0-3.0 wt% per mass of hydrocarbon liquid. Also, under normal circumstances, the amount of detergent added to subsequently inhibit nitration of hydrocarbon liquids during operation at bulk liquid temperatures of 60-180°C in the presence of nitrogen dioxide contamination will be in the range of 0.2-5.0 wt.% active ingredient per mass of hydrocarbon liquid; preferably, 0.5-4.0 wt.% active ingredient per mass of hydrocarbon liquid. More preferably, the detergent is added in an amount in the range of 1.0-3.0 wt.% active ingredient per mass of hydrocarbon liquid; most preferably, 1.5-2.5 wt.% active ingredient per mass of hydrocarbon liquid.

[0073] Use of the fifth aspect of the invention A fifth aspect provides the use of a detergent additive comprising one or more hydrocarbyl-substituted neutral or overbased metal salts as an active ingredient to enhance the efficacy of an ionic liquid additive for inhibiting nitration of hydrocarbon liquids due to on-stream nitrogen dioxide contamination, operating at bulk liquid temperatures between 60 and 180° C., said ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive is added to the hydrocarbon fluid containing the ionic liquid additive prior to operation at bulk fluid temperatures between 60 and 180° C. and exposure to nitrogen dioxide contamination.

[0074] Suitable and preferred ionic liquids, detergents and hydrocarbon liquids for all use aspects of the present invention are those previously described herein. The amount of detergent used to improve the effectiveness of the ionic liquid in inhibiting nitrification in this use of the present invention can be determined by routine testing under conditions that replicate or simulate the nitrogen dioxide contamination at high operating temperatures experienced in the system of interest. In a preferred embodiment of this use, the chemical decomposition inhibited by the ionic liquid and promoted by the detergent results from the decomposition of hydrocarbon nitrates formed during operation by nitration of hydrocarbon liquids with nitrogen dioxide at bulk liquid temperatures between 60 and 180°C, and the ionic liquid and detergent inhibit the formation of hydrocarbon nitrates during that operation, thus directly inhibiting the buildup of reactive hydrocarbon nitrate reservoirs at high operating temperatures and better limiting their decomposition.

[0075] In a more preferred embodiment of this use, the chemical decomposition inhibited by the ionic liquid and promoted by the cleaning agent results from the decomposition of hydrocarbon nitrates by periodically or continuously subjecting the hydrocarbon liquid to bulk liquid temperatures of 110-160°C during operation, and the ionic liquid and cleaning agent inhibit the formation of hydrocarbon nitrates during operation, thus directly inhibiting the more rapid and severe decomposition that occurs during operation at high temperatures. In this use embodiment of the invention, as in the fourth aspect, the level of nitrate ester formation in the bulk liquid can be determined spectroscopically by observing the increase over time in the infrared peak height associated with the nitrate ester in the bulk liquid under suitable test conditions. This spectroscopic approach allows for the observation of the increased efficacy of the ionic liquid for inhibiting nitrate ester formation in the bulk liquid in the presence of the detergent. Inhibition of hydrocarbon nitrate ester formation during operation is determined by observing a relatively lower nitrate ester peak height in the bulk liquid in the presence of the ionic liquid and detergent. This peak height is measured by infrared spectroscopy according to DIN 51 453 or ASTM D8048-20, compared to the nitrate ester peak observed with the same amount of ionic liquid active ingredient alone under similar conditions of operation and nitrogen dioxide contamination. According to this DIN method, the nitrate ester peak at 1630 cm -1 The height of the single infrared absorption frequency is 1615 cm -1 and 1645cm -1 The peak height is measured above a linear baseline defined by the absorbance at 1950 cm. The higher the peak height, the more nitrate esters there are in the bulk fluid. By measuring a series of samples taken over time, it is possible to track the change in peak height as the nitrate ester level in the operating fluid changes over time. According to the ASTM D8048-20 standard test method, the oxidation and nitrification peak heights are measured by first subtracting the infrared spectrum of a new fluid. The baseline is measured at 1950 cm. -1 ~1850cm -1 The highest peak is at 1740 cm for oxidation. -1 ~1700cm -1 range, nitrification at 1640 cm -1 ~1620cm -1 The range is.

[0076] However, under normal circumstances, the amount of ionic liquid used to inhibit nitration of hydrocarbon liquids in the presence of nitrogen dioxide contamination and during operation at bulk liquid temperatures of 60-180°C is in the range of 0.1-5.0 wt% per mass of hydrocarbon liquid; preferably, 0.5-4.0 wt% per mass of hydrocarbon liquid. More preferably, the ionic liquid is used in an amount in the range of 1.0-3.5 wt% per mass of hydrocarbon liquid; most preferably, 1.0-3.0 wt% per mass of hydrocarbon liquid. Also, under normal circumstances, the amount of detergent added to increase the effectiveness of the ionic liquid in inhibiting nitrification of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180°C in the presence of nitrogen dioxide contamination is in the range of 0.2 to 5.0 wt.% active ingredient per mass of hydrocarbon liquid; preferably, 0.5 to 4.0 wt.% active ingredient per mass of hydrocarbon liquid. More preferably, the detergent is added in the range of 1.0 to 3.0 wt.% active ingredient per mass of hydrocarbon liquid; most preferably, 1.5 to 2.5 wt.% active ingredient per mass of hydrocarbon liquid.

[0077] Most preferably, the method of the third aspect of the invention, and all other uses of the invention, are aimed at limiting the breakdown of hydrocarbon fluids that are engine lubricants. These fluids are subject to nitrogen dioxide contamination during operation due to exhaust gas blow-through from the combustion chamber, past the piston rings, and into the crankcase. Such fluids, also called crankcase oils, operate at bulk fluid temperatures where the nitrification pathway to oil breakdown becomes prominent, especially when the fluid is new and aged oil components are not being formed in significant amounts by other mechanisms. Engines that operate at relatively high temperatures are particularly susceptible to such breakdown, especially those that experience bulk crankcase oil temperature regimes or cycles between 110°C and 160°C, especially between 130°C and 160°C. In the above method and all uses of the present invention, preferred ionic liquids are those in which one or more anions (ii), more preferably all anions (ii), contain a hydrocarbyl group that is an aromatic ring bearing at least two substituted functional groups containing heteroatoms, the functional groups being conjugated with the aromatic ring, and this conjugated system carries an anionic (negative) charge. Anions of this preferred configuration are believed to have a particularly high affinity for nitrogen dioxide and to be able to bind to nitrogen dioxide in a manner that significantly reduces its reactivity with hydrocarbon compounds.

[0078] The aromatic ring contains carbon and, optionally, one or more heteroatoms, such as nitrogen or oxygen. However, each anion (ii) of the ionic liquid preferably does not contain nitrogen. Such ionic liquids are more advantageous in the present invention, as they have been found to be unable to contribute to the formation of nitrogen dioxide in environments where a portion of the ionic liquid is consumed by combustion, such as in an engine lubricant environment. In a first advantageous form of this preferred embodiment of the anion, the aromatic ring of each anion (ii) bears two substituted functional groups containing heteroatoms. More preferably, the aromatic ring of each anion (ii) of the ionic liquid bears a carboxylate group and, in addition, another heteroatom-containing functional group. More preferably, both heteroatom(s) in both of these functional groups consist of oxygen atoms. More preferably, these functional groups are located on adjacent ring carbon atoms in an "ortho" configuration to each other on the aromatic ring.

[0079] In this embodiment of the anion, each anion (ii) is highly preferably a disubstituted benzene ring having a carboxylate group and a second heteroatom-containing functional group containing only oxygen as the heteroatom, with these two groups preferably positioned in an "ortho" configuration relative to one another on the aromatic ring. Preferably, the second functional group is a hydroxyl group, forming a hydroxybenzoate anion (ii). Most preferably, the one or more anions (ii) of the ionic liquid are one or more salicylate anions, i.e., anions formed from the deprotonation of salicylic acid. In a second, more advantageous form of this preferred embodiment of the anion, the aromatic ring of each anion (ii) of the ionic liquid itself further carries one or more hydrocarbyl substituents, which impart additional hydrophobic properties to the ionic liquid, making it more readily miscible with hydrocarbon-based bulk liquids. The hydrocarbyl substituent(s) added to the aromatic ring of the anion of this second embodiment are as defined above. Preferably, these substituent(s) are alkyl substituents. Suitable alkyl groups include straight- or branched-chain alkyl groups having 6 or more carbon atoms, preferably 6 to 28, and more preferably 6 to 14 carbon atoms. Particularly suitable alkyl substituents include hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, and particularly herein, n-alkyl groups.

[0080] The aromatic ring of anion (ii) of this second embodiment may have single or multiple alkyl substituents. The resulting ionic liquid may comprise a mixture of anions (ii) differing in the number and / or location of the alkyl substituents. The alkyl substituents are preferably selected from those alkyl substituents specified above. Preferably, at least one of the alkyl substituents has at least 10 carbon atoms and is selected from the examples above. More preferably, the aromatic ring of each anion (ii) in the ionic liquid has one or more linear or branched alkyl substituents having more than 10 carbon atoms. In a second more preferred embodiment of the anion, the one or more anions (ii) are hydrocarbyl-substituted hydroxybenzoates, preferably of the following structure: [ka] wherein R is a linear or branched chain hydrocarbyl group, more preferably an alkyl group as defined above, such as a linear or branched chain alkyl group. There may be multiple R groups attached to the benzene ring. The carboxylate group and hydroxyl group are conjugated to the aromatic ring, and this system has a negative (anionic) charge. The carboxylate group can be located in the ortho, meta, or para position relative to the hydroxyl group; the ortho position is preferred. The R group can be located in the ortho, meta, or para position relative to the hydroxyl group.

[0081] In a second anion embodiment, the one or more anions (ii) of the ionic liquid are most preferably one or more alkyl-substituted salicylate anions, wherein the alkyl substituent(s) of each anion are each independently selected from alkyl groups containing 12 to 24 carbon atoms; more preferably, dodecyl, tetradecyl, hexadecyl, and octadecyl. Such hydroxybenzoates and salicylates are typically prepared via the carboxylation of phenoxides by the Kolbe-Schmitt method, and are generally obtained in admixture with uncarboxylated phenol (usually in a dilute solution). Also preferred detergents for the present method and use are those in which the active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted carboxylic acids, more preferably one or more neutral or overbased metal salts of one or more hydroxybenzoic acids. Such carboxylate detergents can be prepared by reacting an aromatic carboxylic acid with a suitable metal compound, such as an oxide or hydroxide, and neutral or overbased products may be obtained by methods well known in the art. The aromatic moiety of the aromatic carboxylic acid can contain heteroatoms, such as nitrogen and oxygen. Preferably, the moiety contains only carbon atoms; more preferably, the moiety contains six or more carbon atoms; for example, benzene is a preferred moiety. The aromatic carboxylic acid may contain one or more aromatic moieties, such as one or more benzene rings, fused or linked via alkylene bridges. The carboxyl moiety may be directly or indirectly attached to the aromatic moiety. Preferably, the carboxylic acid group is attached directly to a carbon atom on the aromatic moiety, such as a carbon atom on a benzene ring. More preferably, the aromatic moiety also contains a second functional group, such as a hydroxy group or a sulfonate group, which can be attached directly or indirectly to a carbon atom on the aromatic moiety.

[0082] Preferred examples of aromatic carboxylic acids include salicylic acid and its sulfurized derivatives, such as hydrocarbyl-substituted salicylic acid and its derivatives. For example, methods for sulfurizing hydrocarbyl-substituted salicylic acid are known to those skilled in the art. Salicylic acid is typically prepared by carboxylation of phenoxides, for example, using the Kolbe-Schmitt method, and is generally obtained in admixture with uncarboxylated phenol, usually in a diluent. Preferred substituents in oil-soluble salicylic acids are alkyl substituents. In alkyl-substituted salicylic acids, the number of carbon atoms in the alkyl group is advantageously 5 to 100, preferably 9 to 30, and especially 14 to 20. When there are multiple alkyl groups, the average number of carbon atoms in all the alkyl groups is preferably at least 9 to ensure sufficient oil solubility.

[0083] In this aspect of the invention, it is particularly preferred that the detergent active ingredient is one or more alkaline earth metal salts of alkyl-substituted salicylic acids, most preferably one or more magnesium salts of alkyl-substituted salicylic acids. In both such embodiments, it is most preferred that the alkyl substituent(s) of each salicylate comprising the detergent active ingredient are each independently selected from alkyl groups containing from 9 to 30 carbon atoms, especially from 14 to 20 carbon atoms. In the practice of this invention, detergents containing magnesium salts are preferred. In this aspect of the invention, the magnesium detergent may be the sole metal-containing detergent, in which case 100% of the metal introduced into the lubricating oil composition by the detergent is magnesium. When an overbased or neutral detergent based on a metal other than magnesium is employed, preferably at least about 30 wt. %, more preferably at least about 40 wt. %, and especially at least about 50 wt. % of the total metal introduced into the lubricating oil composition by the detergent is magnesium.

[0084] The present invention further relates to: 1. An additive composition for hydrocarbon fluids, the additive composition comprising an ionic liquid and a detergent additive, the ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts; the additive composition further comprises a carrier fluid or diluent. Additive composition. 2. A hydrocarbon liquid composition, said hydrocarbon liquid composition comprising a major amount of a hydrocarbon liquid and a minor amount of an ionic liquid and a detergent additive, said ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts, Hydrocarbon liquid compositions. 3. The composition of paragraph 1 or 2, wherein each cation (i) of the ionic liquid contains nitrogen. 4. The composition of paragraph 3, wherein each cation (i) comprises a substituted ammonium cation or an alicyclic or aromatic ring system incorporating nitrogen and bearing a cationic charge. 5. The composition of paragraph 3 or 4, wherein each cation (i) is a tetrasubstituted ammonium cation. 6. The composition of paragraph 5, wherein each cation (i) of the ionic liquid does not contain nitrogen. 7. The composition of paragraph 6, wherein each cation (i) of the ionic liquid consists of a tetrahydrocarbyl-substituted central atom or ring system bearing a cationic charge. 8. The composition of paragraph 7, wherein each cation (i) of the ionic liquid is a tetraalkyl-substituted phosphonium cation. 9. The composition of any of paragraphs 1 to 8, wherein each anion (ii) of the ionic liquid does not contain nitrogen. 10. The composition of any of paragraphs 1 to 9, wherein each anion (ii) of the ionic liquid comprises a carboxylate functional group. 11. The composition of paragraph 10, wherein each anion (ii) of the ionic liquid is a hexanoate anion. 12. The composition of paragraph 10, wherein each anion (ii) of the ionic liquid comprises a carboxylate group and further comprises a heteroatom-containing functional group. 13. The composition of paragraph 12, wherein each anion (ii) of the ionic liquid comprises a hydrocarbyl group that is an aromatic ring, the ring bearing a carboxylate group and further heteroatom-containing functional groups, which functional groups are conjugated with the aromatic ring, and the conjugated system bearing an anionic charge. 14. The composition of paragraph 13, wherein the one or more anions (ii) of the ionic liquid are one or more salicylate anions. 15. The composition of paragraph 13, wherein the aromatic ring of each anion (ii) of the ionic liquid further comprises one or more straight or branched chain alkyl substituents. 16. The composition of paragraph 15, wherein the one or more anions (ii) of the ionic liquid are one or more alkyl-substituted salicylate anions, and the alkyl substituent(s) of each anion are each independently selected from alkyl groups having from 12 to 24 carbon atoms. 17. The composition of any of paragraphs 11, 14, and 16, wherein each cation (i) of the ionic liquid is a trihexyltetradecyl-phosphonium cation. 18. The composition of any of paragraphs 1-17, wherein the detergent active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted aromatic acids or phenols. 19. The composition of paragraph 18, wherein the detergent active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted benzenesulfonic acids. 20. The composition of paragraph 18, wherein the detergent active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted hydroxybenzoic acids. 21. The composition of paragraph 20, wherein the detergent active ingredient is one or more alkaline earth metal salts of alkyl-substituted salicylic acids. 22. The composition of paragraph 21, wherein the detergent active ingredient is one or more magnesium salts of alkyl-substituted salicylic acids. 23. The composition of paragraph 21 or 22, wherein the alkyl substituent(s) of each salicylate salt comprising the cleaning active ingredient are each independently selected from alkyl groups containing 9 to 30 carbon atoms. 24. The composition of any of paragraphs 1 to 23, further comprising an ashless dispersant additive, preferably a phosphorus-containing compound. 25. Paragraph 2, or the composition of any of paragraphs 3 to 24 when read in conjunction with paragraph 2, wherein the hydrocarbon fluid is a lubricating oil, more preferably a crankcase lubricating oil for an internal combustion engine. 26. A method for limiting chemical decomposition of hydrocarbon liquids during operation at bulk liquid temperatures between 60 and 180°C, said decomposition being initiated by nitration of the liquid resulting from nitrogen dioxide contamination during operation, said method comprising: preparing or obtaining a freshly prepared hydrocarbon liquid suitable for operation at a bulk liquid temperature of 60 to 180°C and free of aging components and nitrogen dioxide contamination; and adding an ionic liquid and a detergent additive to the hydrocarbon liquid prior to operation at a bulk liquid temperature of 60 to 180°C, wherein the ionic liquid: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; thereafter adding said ionic liquid and detergent active ingredient in amounts cooperatively effective to inhibit nitration of the hydrocarbon liquid while operating at a bulk liquid temperature of 60 to 180°C in the presence of nitrogen dioxide contamination; and subjecting said hydrocarbon liquid to operation, whereby the ionic liquid and detergent additives limit chemical decomposition of the resulting liquid. Including, method. 27. The method of paragraph 26, wherein the chemical decomposition is due to decomposition of hydrocarbon nitrate esters formed during operation by nitration of the hydrocarbon liquor with nitrogen dioxide at a bulk liquor temperature of 60°C to 180°C; and wherein the ionic liquid and detergent active ingredient are added in amounts determined to inhibit the formation of hydrocarbon nitrate esters during operation. 28. The method of paragraph 27, wherein the decomposition of hydrocarbon nitrate esters results from subjecting the hydrocarbon liquid to bulk liquid temperatures of 110-160°C periodically or continuously during operation; and wherein the ionic liquid and detergent active ingredient are added during said operation in amounts determined to inhibit the formation of hydrocarbon nitrate esters. 29. The method of paragraph 27 or 28, wherein inhibition of hydrocarbon nitrate ester formation during operation is determined by observing a lower nitrate ester peak area in the combined presence of the ionic liquid and detergent active ingredient compared to the nitrate ester peak observed with the same amount of ionic liquid or detergent active ingredient alone, respectively, as measured by infrared spectroscopy in accordance with DIN 51 453 or ASTM D8048-20 under similar conditions of operation and nitrogen dioxide contamination. 30. The method of any of paragraphs 26 to 29, wherein the amounts of ionic liquid and detergent active ingredient added to the hydrocarbon liquid to cooperatively achieve nitrification inhibition are 0.1 to 5.0 wt. % of the ionic liquid per weight of the hydrocarbon liquid and 0.2 to 5.0 wt. % of the detergent active ingredient per weight of the hydrocarbon liquid. 31. The method of any one of paragraphs 26 to 30, wherein the ionic liquid and detergent additive are added in the form of an additive composition according to paragraph 1, or, when read in conjunction with paragraph 1, any one of paragraphs 3 to 24. 32. The method of any of paragraphs 26 to 31, wherein the hydrocarbon liquid is a lubricating oil. 33. The use of an ionic liquid in conjunction with a detergent additive to limit chemical decomposition of a hydrocarbon liquid during operation at bulk liquid temperatures between 60 and 180°C, wherein the ionic liquid: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; The chemical destruction is initiated by nitrification of hydrocarbon liquids resulting from nitrogen dioxide contamination during operation; The ionic liquid and detergent additives are added to an aging component- and nitrogen dioxide-free hydrocarbon liquid prior to operation, and thereafter the ionic liquid and detergent active ingredients inhibit nitrification of the hydrocarbon liquid during operation at bulk liquid temperatures of 60-180°C in the presence of nitrogen dioxide contamination. Collaborative use. 34. The use according to paragraph 33, wherein the ionic liquid and detergent additive are added in the form of an additive composition according to paragraph 1, or, when read together with paragraph 1, any of paragraphs 3 to 24. 35. Use of a detergent additive comprising one or more hydrocarbyl-substituted neutral or overbased metal salts as an active ingredient to enhance the efficacy of an ionic liquid additive for inhibiting nitration of hydrocarbon liquids due to nitrogen dioxide contamination at operation at bulk liquid temperatures between 60 and 180°C, said ionic liquid comprising: (i) one or more organic cations, each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Includes; The detergent additive is added to the hydrocarbon fluid containing the ionic liquid additive prior to operation at bulk fluid temperatures between 60 and 180°C and exposure to nitrogen dioxide contamination. 36. The use according to any of paragraphs 33 to 35, wherein the hydrocarbon liquid is a lubricating oil. 37. A method or use according to any one of paragraphs 26 to 36, wherein the detergent active ingredient has the characteristics specified in any one of paragraphs 18 to 23 and the ionic liquid has the characteristics specified in any one of paragraphs 3 to 17. 38. A method or use according to any one of paragraphs 26 to 37, wherein the detergent active ingredient has the characteristics specified in any one of paragraphs 20 to 23. 39. A method or use according to any one of paragraphs 26 to 38, wherein the ionic liquid has the characteristics specified in any one of paragraphs 13 to 17. 40. A method or use according to any of paragraphs 26 to 39, wherein the hydrocarbon liquid resulting from said method or use further comprises an ashless dispersant additive, and preferably a phosphorus-containing compound. [Example]

[0085] The practice and advantages of the present invention will now be illustrated with reference to the following examples. For purposes of this invention and the claims thereto, the amount of reduction or limitation of nitrate ester formation in a lubricating oil composition is determined by observing that the nitrate ester peak height in the presence of a lubricating oil composition containing an ionic liquid is lower (e.g., at least 10%, such as at least 20%, such as at least 30%, such as at least 40%, such as at least 50%, such as 100% lower) (compared to the nitrate ester peak of the same lubricating oil composition in which the ionic liquid has been replaced with an ionic liquid having the same cation but the same proportion of hexanoate as the anion), as measured by infrared spectroscopy under similar conditions of operation and nitrogen dioxide contamination in accordance with DIN 51 453 or ASTM D8048-20, except that in the event of a conflict between DIN 51 453 and ASTM D8048-20, DIN 51 453 shall be followed.

[0086] Example 1 - Preparation of ionic liquids for use in the working examples Ionic liquids were synthesized using the following method of incorporating ion exchange resins.

[0087] Example 1.1: [P66614] [Salicylate] (Example of an Ionic Liquid of the Present Invention) A two-step synthesis method was used to generate [P66614][salicylate] starting from commercially available trihexyltetradecylphosphonium chloride, [P66614][Cl] (CYPHOS IL-101, >95%, CAS number: 258864-54-9). In the first step, [P66614][OH] was synthesized from [P66614][Cl] using a commercially available basic anion exchange resin (Amberlite IRN-78, OH form resin, CAS number: 11128-95-3). [P66614][Cl] (100 g, 0.193 mol) was added to a 2 L round-bottom flask and diluted with absolute ethanol (900 mL, 19.5 mol, CAS number: 64-17-5). To this was added 100 g of ion exchange resin, and the mixture was stirred at 22 °C for 5 h. The resin was then filtered off, and 100 g of fresh resin was added. This process was repeated three times or until a negative silver halide test was observed, indicating the completion of the ion exchange.

[0088] The silver halide test was performed as follows: A small aliquot (0.2 mL) of the reaction mixture was transferred to a 2 mL vial and diluted with 1 mL of absolute ethanol. Two to three drops of HNO3 were added to acidify the solution, followed by two to three drops of saturated aqueous AgNO3 (≥99% by weight, Sigma-Aldrich, CAS No. 7761-88-8). The ion exchange was complete when a clear solution without precipitate was observed. In the second stage, 1 The concentration of [P66614][OH] in ethanol was measured by H NMR. Then, an equimolar amount of commercially available salicylic acid (≥99.0% by mass, CAS number: 69-72-7) dissolved in 100 mL of ethanol (26.6 g, 0.193 mol of salicylic acid as a 100% yield) was added dropwise, followed by stirring overnight at 22°C. The solution was then dried by rotary evaporation, followed by filtration under reduced pressure (10 -3 Pa) and dried at 50°C for more than 96 hours to obtain a dry pure ionic liquid (determined by NMR as follows). [P66614][Salicylate]: 1 H NMR (500MHz, DMSO‐d6): δ(ppm)=0.87(s,12H,CH3‐‐(P)),1.24~1.58(m,48H,‐CH2‐(P)),2.17(s,8H,‐CH2‐(P)),6.62(m,2H),7.17(m,1H),7.65(m,1H); 13 C NMR (126MHz, DMSO-d6): δ(ppm)=13.86,13.95,17.14,17.28,17.56,17.65,20.50,21.81,22.10,28.0 8,28.63,28.72,28.96,29.05,29.68,29.80,30.40,31.30,116.00,129.92,131.97,162.79,171.31.

[0089] Example 1.2: [P66614] [Alkyl-Salicylate] (Example of an Ionic Liquid of the Present Invention) [P66614][Alkyl-salicylate] was synthesized by the procedure used for [P66614][salicylate] in Example 1.1. First, [P66614][OH] was prepared from [P66614][Cl] (100 g, 0.193 mol). The alkyl-salicylic acid used in the second step instead of the salicylic acid in Example 1.1 was a commercially available sample from Infineum UK Ltd, which is a mixture of mono-alkyl salicylates with alkyl substituents containing 14 and 16 carbon atoms. In this case, the acid value of the salicylic acid (0.00261 gH + The amount of acid (equimolar) required for the neutralization reaction was calculated using the calculated equimolar amount of acid (equimolar) and found to be 73.96 g. After drying, the material was characterized by NMR. [P66614][Alkyl-salicylate]: 1H NMR (500MHz, DMSO‐d6): δ(ppm)= 0.69~0.88(s),1.04~1.29(m),1.37(m),1.46(m),2.15(m),2.29(s),3.34(s),3.43(m),4.36(s),6.49(m),6.7 2(m),6.93(m),7.18(m),7.25(m),7.41(s),7.47(m),7.65(s),7.70(s),8.16(s),9.07(s),9.11(s),9.15(s).

[0090] Another sample of [P66614] [alkyl-salicylate] was prepared by the following scaled-up procedure. [P66614][Cl] (808 g, 1.56 mol) was charged to a 5 L glass reactor and diluted with absolute ethanol (770 mL, 13.2 mol). A solution of KOH (87.3 g, 1.56 mol) previously prepared in absolute ethanol (770 mL, 13.2 mol) was added to the solution over 28 min using a water bath to limit the exotherm to 23 °C. The mixture was aged for 90–250 min, blended with Celite filter aid (164 g, 20 wt%), filtered to remove KCl, and the filter cake was rinsed with absolute ethanol (160 mL, 2.74 mol). The filtrate was transferred to a clean 5 L glass reactor and treated with Amberlite ion exchange resin IRN-78 (400 g, 50 wt%) for 30–70 min. After filtration, the resin was rinsed with absolute ethanol (2 × 160 mL, 2 × 2.74 mol). The filtrate was transferred to a clean 5 L glass reactor, and an equimolar amount of the same alkyl-salicylic acid as a xylene solution was added to the filtrate over 33 min using a water bath to limit the exotherm to 28 °C. The mixture was aged for 16 h, after which the volatile components were removed by rotary evaporation at 60-80 °C and 10 mbar over 3 h.

[0091] Example 1.3: [P66614][Hexanoate] (Example of an Ionic Liquid of the Present Invention) [P66614][hexanoate] was synthesized using the procedure used for [P66614][salicylate] in Example 1.1. First, [P66614][OH] was prepared from [P66614][Cl] (100 g, 0.193 mol). In the second step, an equimolar amount of hexanoic acid (≥99 wt%, CAS No.: 142-62-1) was added (22.4 g, 0.193 mol) in place of salicylic acid to produce the desired ionic liquid, which was then dried.

[0092] Example 1.4: [P66614][NTf2] (Comparative Example) Trihexyltetradecylphosphonium chloride, [P66614][Cl] (100 g, 0.193 mol) was dissolved in a minimum amount of dichloromethane (>99%, CAS No.: 75-09-2) in a 1 L round-bottom flask. To this was added dropwise an aqueous solution of commercially available LiNTf2 (55.3 g, 0.193 mol; 99% by weight, CAS No.: 90076-65-6). The reaction mixture was stirred at 22 °C for 12 h to form a biphasic solution. The organic layer was extracted and washed five times with ultrapure water to remove LiCl by-product and until a negative halide test was obtained. The solution was then dried under rotary evaporation and then eluted under reduced pressure (10 -3 The resulting mixture was dried at 50°C for at least 96 hours under reduced pressure to give pure trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide, [P66614][NTf2], as determined by NMR: [P66614][NTf2]: 1 H NMR (500MHz, CDCl3): δ(ppm)=0.88(m,12H,CH3--(P)),1.23~1.29(m,32H,-CH2-(P)),1.46(m,16H,-CH2-(P)),2.08(m,8H,-CH2-(P)); 13 C NMR(126MHz,CDCl3):δ(ppm)=13.85,14.12,18.56,18.94,21.55,22.28,22.69, 28.80,29.25,29.36,29.49,29.65,30.17,30.52,30.89,31.92,118.62,121.17. These synthetically prepared ionic liquids were used in further examples below.

[0093] Example 2 - Detergent and Dispersant Additives for Use in the Examples The following additional additives were prepared for use in the examples:

[0094] Example 2.1: Calcium Alkyl Sulfonate Detergent, 300 TBN (Detergent of the Invention) In Example 2.1, calcium alkylsulfonate was produced by reacting an alkylsulfonic acid with calcium hydroxide in refluxing toluene in the presence of methanol containing a small amount of water, followed by blowing carbon dioxide into the reaction vessel, further refluxing, a heat soak period followed by dilution and distillation of the base oil, cooling and centrifugation to remove solids, and finishing by removal of the solvent under vacuum.

[0095] Example 2.2: Calcium Alkyl Salicylate Detergent, 350 TBN (Preferred Detergent of the Invention) In Example 2.2, calcium alkyl-salicylate was produced by reacting alkyl-salicylic acid with calcium hydroxide in refluxing xylene in the presence of methanol containing a small amount of water, followed by blowing carbon dioxide into the reaction vessel at the same temperature and further refluxing, followed by cooling and centrifugation to remove the solids, and finishing by removing the solvent under vacuum. The product was diluted in base oil for easy handling.

[0096] Example 2.3: Thermal Polyisobutylene Succinimide Dispersant (Dispersant of the Invention) In Example 2.3, the PIBSA-PAM dispersant was produced in a two-step process by first thermally reacting 2300 g / mole of highly reactive polyisobutylene (PIB) with maleic anhydride to produce PIBSA (polyisobutylene succinic anhydride), and then reacting the PIBSA with an N7 polyamine (PAM) containing approximately 2.3 primary N per mole, resulting in a dispersant with a nitrogen content of approximately 1.2% (as 58% active material).

[0097] Example 2.4: Zinc Dialkyldithiophosphate (Traditional Antioxidant) In Example 2.4, a mixture of primary C8 and secondary C4 alcohols was first prepared with P4S 10 ZDDP (zinc dialkyldiphosphate) was produced in a two-step process by reacting DDPA with zinc oxide to give dialkyldithiophosphate (DDPA), and then reacting the DDPA with a slight excess of zinc oxide to form the final ZDDP. The materials from the above preparations were used in the further examples that follow.

[0098] Example 3 - Evaluation of Ionic Liquid and Detergent Additive Combinations Under Operating Conditions To assess the effectiveness of the benefits of the ionic liquid and cleaning agent combination of the present invention, the initiation and progress of nitrification in a hydrocarbon liquid contaminated with nitrogen dioxide can be observed and measured by infrared spectroscopy. Increases in kinematic viscosity and total acid number (TAN) can also be followed under suitable test conditions to observe other benefits of the present invention. Monitoring the ongoing nitrification of hydrocarbon liquids involves periodically taking samples of the liquid in use under actual or simulated operating conditions and tracking the evolution of the fingerprint region nitrification peak height on the infrared spectrum. The rate of increase in nitrification peak height provides information about the rate of chemical decomposition due to nitrification and accumulation of nitrate reservoirs in the bulk liquid. According to the DIN 51453 peak height method [Standard DIN 51453 (2004-10): Testing of lubricants - Determination of oxidation and nitration of used motor oils - Infrared spectroscopy], a peak at 1630 cm is due to the formation of hydrocarbon nitrate esters. -1 The height of the single infrared absorption frequency is 1615 cm -1 and 1645cm -1 The higher the peak height, the more hydrocarbon nitrate esters there are in the bulk liquid. The DIN method described above identifies the 1710 cm peak attributable to carbonyl moieties (ketones, aldehydes, esters, and carboxylic acids) formed as a result of oxidation. -1The progress of conventional oxidation of the bulk liquid can also be monitored through measurement of the peak height of the 1970 cm -1 and 1650 cm -1 The peak height is measured relative to a linear baseline defined by the absorbance at 1000 kJ / cm2. Again, the rate of increase in peak height provides information about the rate of chemical oxidation in the bulk liquid.

[0099] According to ASTM D8048-20 Standard Test Method for Evaluating Diesel Engine Oils in a Volvo (Mack) T-13 Diesel Engine, the oxidation and nitration peak heights are measured by first subtracting the infrared spectrum of a fresh oil. -1 ~1850cm -1 The highest peak is at 1740 cm for oxidation. -1 ~1700cm -1 range, nitrification at 1640 cm -1 ~1620cm -1 The range is. Samples of hydrocarbon liquids tested under operating conditions can be measured by the above methods to report the effect of different ionic liquids and detergents present in the hydrocarbon liquid on the progress of degradation by nitrification and oxidation, and / or the level of inhibition of that degradation. The increase in kinematic viscosity and the increase in total acid number under test conditions are monitored according to test methods ASTM D445 and ASTM D664, respectively.

[0100] Example 3.1 - Contribution of ionic liquids and detergents to the inhibition of nitrification-induced degradation To illustrate the combined contribution of ionic liquids and detergents in the performance of the present invention, the DIN 51453 method was used. The following test samples were subjected to laboratory simulations of engine lubricant operating conditions. The oil was exposed to sump operating temperatures and a nitrogen dioxide source to mimic operating contamination. This simulation involved a 250 mL three-neck conical flask fitted with a glycol concentrator and heated on an electric hotplate. A gas containing 766 ppm NO2 in air was bubbled through 250 g of the test lubricant at a rate of 10 liters per minute. A sintered glass frit was used to disperse the gas throughout the lubricant. The gas flow rate was regulated using a mass flow controller. A thermocouple was introduced from the third neck back to the hotplate to maintain a constant temperature. Each test sample was run at 130°C for 96 hours, and at the end of the test, the nitration and oxidation peak heights were measured using the DIN 51453 method described above. The results of the two samples containing ionic liquid were then compared to a control oil formulation, and the effect of each ionic liquid was reported as a percentage reduction in nitration and oxidation peak heights relative to the control.

[0101] Tests were conducted on lubricating oils freshly prepared as bulk hydrocarbon fluids. To this starting base oil composition, 2 wt. % of the detergent additives of Examples 2.1 or 2.2, 5 wt. % of the dispersant of Example 2.3, or 1 wt. % of the conventional antioxidant of Example 2.4 were added, per mass of lubricant, to establish a baseline effect on nitration and oxidation of these additives alone. The baseline effect of the ionic liquids of Examples 1.2, 1.3, and 1.4 alone in the same base oil was also established at equimolar levels, corresponding to mass % levels of 2.8 wt. % for Example 1.2, 2.0 wt. % for Example 1.3, or 2.55 wt. % for Example 1.4. The starting base oil composition was also used as a control run to establish a baseline provided by commercially available base oils.

[0102] The results are shown in the table below. result [Table 2]

[0103] Considering the baseline results (Tests 1-5) for the detergents, dispersants, and phosphorus-based antioxidants first, it is clear that the dispersant (Example 2.3) showed no benefit of its own in controlling nitrification under the nitrogen dioxide contamination test conditions, and instead had a detrimental effect on the oxidation aspect of the test, significantly increasing the oxidation peak height (i.e., a negative % reduction). The detergent in Example 2.1 had little effect on both oxidation and nitrification, while the detergent in Example 2.2 only slightly reduced both the oxidation and nitrification peak heights. As expected, the antioxidant in Example 2.4 demonstrated strong antioxidant performance, but significantly less control of nitrification, demonstrating that nitrification of the oil proceeds via a mechanism other than traditional oxidation. Considering the results of equimolar comparisons of ionic liquid alone in base oil (Tests 6-8), it can be seen that the ionic liquid of Example 1.3 does not exhibit nitrification inhibition effects by itself compared to the base oil. In contrast, the preferred ionic liquid of Example 1.2 already exhibits very high nitrification inhibition effects, demonstrating its superior performance as a preferred ionic liquid containing a preferred aromatic carboxylate anion. In contrast to Example 1.3, the preferred Example 1.2 also exhibits very high oxidation activity. The halogen- and sulfur-containing ionic liquid of Example 1.4 exhibits significant antioxidant properties as opposed to a negative effect on nitrification, again demonstrating that nitrification of oil solutions proceeds via a different mechanism.

[0104] Co-addition of the detergents of Examples 2.1 or 2.2 to the comparative ionic liquid of Example 1.4 (Tests 13 and 14) eliminates the antioxidant benefit of the ionic liquid alone (Test 8), resulting in less nitrification control than either detergent would provide alone (Tests 2 and 3). In contrast, co-addition of each detergent to the preferred ionic liquid of Example 1.2 (Tests 9 and 10) further enhances the already high nitrification control without adversely affecting the near-complete antioxidant effect of this ionic liquid (see Test 6). The resulting combination provides excellent combined control of nitrification and oxidation, offering significant advantages to oil formulators seeking to control oil degradation through different mechanisms. Co-addition of the more preferred detergent of Example 2.2 with the less preferred ionic liquid of Example 1.3 results in increased nitrification reduction and antioxidant protection (Test 12), but not to the very high levels achieved with the ionic liquid of Example 1.2. By adding the less preferred cleaning agent of Example 2.1 to the less preferred ionic liquid of Example 1.3 (Test 11), the pro-oxidant effect of this ionic liquid alone is eliminated. The co-addition of a dispersant (Example 2.3) and an antioxidant (Example 2.4) in Tests 15-22 also demonstrated the benefits of the combination of the present invention.

[0105] Co-incorporation of the detergent of Example 2.1 with a dispersant and antioxidant (Test 15) resulted in a smaller nitrification-enhancing effect and a smaller net reduction in oxidation compared to the detergent alone (Test 2). The results indicated that the strong antioxidant effect of Example 2.4 was almost completely neutralized by the dispersant, and the moderate nitrification control of Example 2.4 was nearly eliminated. Thus, this binary combination of additional additives when added to the detergent was not at all significant for nitrification control. However, the further co-incorporation of the preferred ionic liquid of Example 1.2 (Test 16) resulted in a fluid with very high antioxidant properties and excellent nitrification control. This was similarly not negated by the presence of the dispersant. Similarly, co-addition of the ionic liquid of Example 1.3 (Test 17) demonstrated strong antioxidant benefits and appreciable nitrification control, even in the presence of the dispersant. Thus, the combination of the ionic liquids of the present invention with detergents allows for the further inclusion of dispersants without negating the benefits of the present invention for nitrification and oxidation control, allowing for the preparation of oil formulations that can incorporate dispersants for their beneficial effects without making the oil more susceptible to chemical degradation by nitrification and conventional oxidation. In contrast, the co-addition of halogen- and sulfur-containing ionic liquids in Example 1.4 did not provide nitrification control and had significantly less antioxidant effect. Similarly, Tests 19-22 using the more preferred detergent of Example 2.2 demonstrated significantly higher nitrification control (Tests 20 and 21) with this detergent and the ionic liquids of Examples 1.2 and 1.3, even in the presence of a dispersant, and despite a clear decrease in baseline net nitrification control for the detergent of Example 2.2 in the presence of a dispersant and the conventional antioxidant of Example 2.4 (Test 19). Also, in contrast, the halogen- and sulfur-containing ionic liquid of Example 1.4 provided significantly less nitrification control and antioxidant protection. Thus, these preferred formulations impart the dispersancy benefits of Example 2.3 to the oil, while inhibiting increased oil nitrification in the presence of nitrogen dioxide contamination and providing the added antioxidant benefits.

[0106] The superior performance of the ionic liquid of Example 1.2 over Example 1.3 was maintained in these combination tests, confirming that the ionic liquid of the Example 1.2 type is the most preferred. Similarly, the effectiveness of the cleaning agent of Example 2.2, which was found to be superior to that of Example 2.1, confirmed that the Example 2.2 type is the most preferred.

[0107] Example 3.2 - Contribution of Ionic Liquids and Detergents to Dynamic Viscosity Control The increase in kinematic viscosity (at 40°C) of hydrocarbon oils under nitrogen dioxide-contaminated conditions was measured using the ASTM D445 standard test method. Briefly, this standard method involves measuring the time it takes for a determined volume of liquid to flow under gravity through a calibrated glass capillary viscometer under a reproducible drive head at a controlled temperature. Kinematic viscosity is determined from the viscometer calibration constant and the liquid flow time. Each test run was performed using the example additive combination listed in the figure, and in each case the amount of example additive(s) used in the fluid was the same as in Example 3.1. The results of the test are shown in Figure 1 as the kinematic viscosity achieved at the end of the test expressed as a percentage of the viscosity exhibited by the base oil at the end of the test. Thus, a result below 100% indicates less viscosity increase than the base oil, while a result above 100% indicates more viscosity increase. Minimal viscosity increase indicates that the fluid is more resistant to degradation under the test conditions.

[0108] Reading the results in Figure 1 from bottom to top, these tests first illustrate that the detergents of Examples 2.1 and 2.2 by themselves reduced viscosity increase compared to the base oil, while the dispersant of Example 2.3 by itself slightly increased viscosity. The antioxidant of Example 2.4 by itself showed a strong reduction in viscosity increase. The ionic liquids of Examples 1.2 and 1.3 by themselves both reduced viscosity increase, with the preferred Example 1.2 providing a much greater benefit that was maintained in the presence of the detergents of Examples 2.1 and 2.2. The addition of each of these detergents to the ionic liquid of Example 1.3 significantly reduced viscosity increase compared to the ionic liquid alone, and with the preferred detergent of Example 2.2, this ionic liquid performed at essentially the same level as the combination including the preferred ionic liquid of Example 1.2. The corresponding binary combination of detergent and ionic liquid of Example 1.4 (comparative example) provided a smaller viscosity improvement.

[0109] The addition of detergents, dispersants, and antioxidants to the base oils resulted in viscosity increases that were less than those seen with the base oils, but still greater than those seen with the antioxidant alone in Example 2.4, indicating that the presence of the dispersant somewhat inactivated viscosity control in these combinations. However, the further co-addition of the ionic liquids of Examples 1.2 or 1.3 to these combinations resulted in a more significant reduction in viscosity increase. This demonstrates that the combinations of the present invention achieve high levels of viscosity reduction even in the presence of dispersants, allowing the use of dispersants simultaneously with the viscosity control provided by the combination of ionic liquids and detergents.

[0110] Example 3.3 - Contribution of Ionic Liquids and Detergents to Total Acid Number Control The increase in total acid number (TAN) of hydrocarbon oils under nitrogen dioxide contaminated conditions was measured using the ASTM D664 standard test method, which briefly involves subjecting test samples to potentiometric titration with potassium hydroxide to determine the amount of acidic substance(s) present in the oil solution. Each test run was performed using the example additive combination listed in the figure, and in each case the amount of example additive(s) used in the fluid was the same as in Example 3.1. The results of the test are shown in Figure 1 as the TAN achieved at the end of the test expressed as a percentage of the TAN exhibited by the base oil at the end of the test. Thus, a result below 100% indicates less TAN gain than the base oil, while a result above 100% indicates more TAN gain. The least TAN gain indicates that the oil is more resistant to increased acidity and subsequent degradation under the test conditions. Reading the results in Figure 1 from bottom to top, these tests first illustrate that the detergents of Examples 2.1, 2.2, and 2.3 by themselves reduced TAN gain compared to the base oil, and the antioxidant of Example 2.4 by itself strongly reduced TAN gain.

[0111] The ionic liquids of Examples 1.2 and 1.3 by themselves both reduced TAN gain, with preferred Example 1.2 providing essentially complete control that was maintained in the presence of the detergents of Examples 2.1 and 2.2. The addition of each of these detergents to the ionic liquid of Example 1.3 significantly reduced TAN gain even further than the ionic liquid alone, and with the preferred detergent of Example 2.2, this ionic liquid performed at a level similar to the combination including the preferred ionic liquid of Example 1.2. The corresponding binary combination of detergent and ionic liquid of Example 1.4 (comparative example) provided less improvement in TAN. The addition of detergents, dispersants, and antioxidants to the base oil resulted in a TAN increase that was less than that seen with the base oil, but still greater than the viscosity increase seen with the antioxidant alone in Example 2.4. However, the further co-addition of ionic liquids in Examples 1.2 or 1.3 to these combinations resulted in a more significant reduction in TAN increase. This demonstrates that the combinations of the present invention provide high levels of viscosity reduction even in the presence of dispersants, allowing the use of dispersants in conjunction with the TAN control provided by the combination of ionic liquids and detergents. Thus, throughout these examples, the benefits of the combination of the present invention are seen in one or more of nitrification control, oxidation control, viscosity increase, and TAN increase.

[0112] All documents described herein are incorporated by reference, including any priority documents and / or testing procedures, to the extent not inconsistent therewith. While aspects of the invention have been illustrated and described, as is apparent from the foregoing general description and specific embodiments, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited by such modifications. The term "comprising" specifies the presence of stated features, steps, integers, or components, but does not exclude the presence or addition of one or more other features, steps, integers, components, or groups thereof. Similarly, the term "comprising" is considered synonymous with the term "including." Similarly, whenever a composition, element, or group of elements is preceded by the transitional phrase "comprising," it is to be understood that the same composition or group of elements can also be preceded by the transitional phrase "consisting essentially of," "consisting of," "selected from the group consisting of," or "is," and vice versa. Furthermore, if a range is stated as being between A and B, the range includes the endpoints A and B, and therefore "between A and B" is synonymous with "from A to B."

Claims

1. 1. An additive composition for hydrocarbon fluids, the additive composition comprising an ionic liquid and a detergent additive, the ionic liquid comprising: (i) one or more organic cations each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Including; An additive composition wherein the detergent additive comprises, as an active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts; and the additive composition further optionally comprises a carrier fluid or diluent.

2. 1. A hydrocarbon liquid composition, said hydrocarbon liquid composition comprising a predominant amount of a hydrocarbon liquid, and a minor amount of a detergent additive and a minor amount of an ionic liquid, said ionic liquid comprising: (i) one or more organic cations each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Including; The detergent additive is a hydrocarbon liquid composition comprising, as an active ingredient, one or more neutral or overbased hydrocarbyl-substituted metal salts.

3. 3. The composition of claim 1 or 2, wherein each said cation (i) of said ionic liquid contains nitrogen.

4. 4. The composition of claim 3, wherein each said cation (i) comprises a substituted ammonium cation or an alicyclic or aromatic ring system incorporating nitrogen and bearing a cationic charge.

5. 4. The composition of claim 3, wherein each said cation (i) is a tetrasubstituted ammonium cation.

6. 6. The composition of claim 5, wherein each said cation (i) of said ionic liquid is nitrogen-free.

7. 7. The composition of claim 6, wherein each said cation (i) of said ionic liquid consists of a tetrahydrocarbyl-substituted central atom or ring system bearing a cationic charge.

8. 8. The composition of claim 7, wherein each said cation (i) of said ionic liquid is a tetraalkyl-substituted phosphonium cation.

9. 3. The composition of claim 1 or 2, wherein each anion (ii) of the ionic liquid is nitrogen-free.

10. 3. The composition of claim 1 or 2, wherein each anion (ii) of the ionic liquid comprises a carboxylate functional group.

11. 11. The composition of claim 10, wherein each anion (ii) of the ionic liquid is a hexanoate anion.

12. 11. The composition of claim 10, wherein each anion (ii) of the ionic liquid comprises a carboxylate group and further comprises a heteroatom-containing functional group.

13. 13. The composition of claim 12, wherein each anion (ii) of the ionic liquid comprises a hydrocarbyl group that is an aromatic ring, the ring bearing a carboxylate group and further heteroatom-containing functional groups that are conjugated with the aromatic ring, the conjugated system bearing an anionic charge.

14. 14. The composition of claim 13, wherein the one or more anions (ii) of the ionic liquid are one or more salicylate anions.

15. 14. The composition of claim 13, wherein the aromatic ring of each anion (ii) of the ionic liquid further comprises one or more straight or branched chain alkyl substituents.

16. 16. The composition of claim 15, wherein the one or more anions (ii) of the ionic liquid are one or more alkyl-substituted salicylate anions, wherein the alkyl substituents of each anion are each independently selected from alkyl groups containing from 12 to 24 carbon atoms.

17. 11. The composition of claim 10, wherein each said cation (i) of said ionic liquid is a trihexyltetradecyl-phosphonium cation.

18. 3. The composition of claim 1 or 2, wherein the detergent-active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted aromatic acids or phenols.

19. 20. The composition of claim 18, wherein the detergent-active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted benzenesulfonic acids.

20. 20. The composition of claim 18, wherein the detergent-active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted hydroxybenzoic acids.

21. 21. The composition of claim 20, wherein the detergent active ingredient is one or more alkaline earth metal salts of alkyl-substituted salicylic acids.

22. 22. The composition of claim 21, wherein the detergent active is one or more magnesium salts of alkyl-substituted salicylic acids.

23. 22. The composition of claim 21, wherein the alkyl substituents of each salicylate comprising the cleaning active ingredient are each independently selected from alkyl groups containing from 9 to 30 carbon atoms.

24. 3. The composition of claim 1 or 2, further comprising an ashless dispersant additive, preferably a phosphorus-containing compound.

25. 3. The composition of claim 2, wherein the hydrocarbon fluid is a lubricating oil, more preferably a crankcase lubricating oil for an internal combustion engine.

26. 1. A method for limiting chemical decomposition of a hydrocarbon liquid during operation at bulk liquid temperatures between 60 and 180°C, said decomposition being initiated by nitrification of said liquid resulting from nitrogen dioxide contamination during operation, said method comprising: preparing or obtaining a freshly prepared hydrocarbon liquid suitable for operation at a bulk liquid temperature of 60 to 180°C and free of aged components and nitrogen dioxide contamination; and adding an ionic liquid and a detergent additive to the hydrocarbon liquid prior to operation at a bulk liquid temperature of 60 to 180°C, wherein the ionic liquid: (i) one or more organic cations each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Including; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; thereafter adding said ionic liquid and detergent active ingredient in amounts cooperatively effective to inhibit nitration of said hydrocarbon liquid while operating at a bulk liquid temperature of 60-180°C in the presence of nitrogen dioxide contamination; and subjecting the hydrocarbon liquid to operation, whereby the ionic liquid and the detergent additive limit any resulting chemical decomposition of the liquid. A method comprising:

27. 27. The method of claim 26, wherein the chemical decomposition results from decomposition of hydrocarbon nitrate esters formed during operation by nitration of the hydrocarbon liquor with nitrogen dioxide at bulk liquor temperatures of 60 to 180°C; and the ionic liquid and the detergent active ingredient are added in amounts determined to inhibit the formation of the hydrocarbon nitrate esters during operation.

28. 28. The method of claim 27, wherein the decomposition of the hydrocarbon nitrate esters results from subjecting the hydrocarbon liquid to bulk liquid temperatures of 110-160°C periodically or continuously during operation; and wherein the ionic liquid and the detergent active ingredient are added during the operation in amounts determined to inhibit the formation of the hydrocarbon nitrate esters.

29. 29. The method of claim 27 or 28, wherein the inhibition of hydrocarbon-based nitrate ester formation during operation is determined by observing a lower nitrate ester peak area in the combined presence of the ionic liquid and the detergent active ingredient compared to the nitrate ester peak observed with the same amount of ionic liquid or detergent active ingredient alone, respectively, wherein the peak area is measured by infrared spectroscopy according to DIN 51 453 or ASTM D8048-20 under similar conditions of operation and nitrogen dioxide contamination.

30. 27. The method of claim 26, wherein the amount of ionic liquid and detergent active ingredient added to the hydrocarbon liquid to cooperatively achieve nitrification inhibition is 0.1 to 5.0 wt. % of the ionic liquid per weight of the hydrocarbon liquid and 0.2 to 5.0 wt. % of the detergent active ingredient per weight of the hydrocarbon liquid.

31. 27. The method of claim 26, wherein the ionic liquid and the detergent additive are added in the form of the additive composition of claim 1.

32. 27. The method of claim 26, wherein the hydrocarbon liquid is a lubricating oil.

33. 1. The cooperative use of an ionic liquid and a detergent additive to limit chemical decomposition of a hydrocarbon liquid during operation at bulk liquid temperatures between 60 and 180° C., wherein the ionic liquid comprises: (i) one or more organic cations each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Including; The detergent additive comprises, as an active ingredient, one or more hydrocarbyl-substituted neutral or overbased metal salts; The chemical destruction is initiated by nitrification of hydrocarbon liquids resulting from nitrogen dioxide contamination during operation; 1. The cooperative use of the ionic liquid and the detergent additive to the hydrocarbon liquid free of aging components and nitrogen dioxide prior to operation, whereby the ionic liquid and the detergent active ingredient inhibit nitrification of the hydrocarbon liquid during operation at bulk liquid temperatures of 60-180°C in the presence of nitrogen dioxide contamination.

34. 34. The use of claim 33, wherein the ionic liquid and the detergent additive are added in the form of the additive composition of claim 1.

35. 1. Use of a detergent additive comprising one or more hydrocarbyl-substituted neutral or overbased metal salts as an active ingredient to enhance the efficacy of an ionic liquid additive for inhibiting nitration of hydrocarbon liquids due to nitrogen dioxide contamination at operation at bulk liquid temperatures of 60 to 180°C, said ionic liquid comprising: (i) one or more organic cations each containing a central atom or ring system bearing a cationic charge and a plurality of pendant hydrocarbyl substituents; and (ii) one or more halogen-, sulfur-, and boron-free organic anions each containing one or more heteroatom-containing functional groups and one or more hydrocarbyl groups having a localized or delocalized anionic charge; Including; The detergent additive is added to the hydrocarbon fluid containing the ionic liquid additive prior to operation at bulk fluid temperatures of 60-180° C. and exposure to nitrogen dioxide contamination.

36. 36. The use according to claim 33 or 35, wherein the hydrocarbon liquid is a lubricating oil.

37. 36. The method or use of claim 26, 33 or 35, wherein the detergent-active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted aromatic acids or phenols, and each of said cations (i) of the ionic liquid contains nitrogen.

38. 36. The method or use of claim 26, 33 or 35, wherein the detergent active ingredient is or comprises one or more neutral or overbased metal salts of one or more hydrocarbyl-substituted hydroxybenzoic acids.

39. 36. The method or use of claim 26, 33 or 35, wherein each anion (ii) of the ionic liquid comprises a hydrocarbyl group which is an aromatic ring, said ring bearing a carboxylate group and further heteroatom-containing functional groups which are conjugated with said aromatic ring, this conjugated system carrying an anionic charge.

40. 36. The method or use of claim 26, 33 or 35, wherein the hydrocarbon liquid resulting from the method or use further comprises an ashless dispersant additive, and preferably a phosphorus-containing compound.