Patent Publication Number: US-2005132641-A1

Title: Fuel lubricity from blends of lubricity improvers and corrosion inhibitors or stability additives

Description:
FIELD OF THE INVENTION  
      The present invention relates to lubricity additives for distillate fuels, and more particularly relates, in one embodiment to the co-use of corrosion inhibitors and/or stability additives together with lubricity additives for hydrocarbon fuels.  
     BACKGROUND OF THE INVENTION  
      It is well known that in many engines the fuel is the lubricant for the fuel system components, such as fuel pumps and injectors. Many studies of fuels with poor lubricity have been conducted in an effort to understand fuel compositions that have poor lubricity and to correlate lab test methods with actual field use. The problem is general to diesel fuels, kerosene and gasolines, however, most of the studies have concentrated on the first two hydrocarbons.  
      Previous work has shown that saturated, monomeric and dimeric, fatty acids of from 12 to 54 carbon atoms used individually give excellent performance as fuel lubricity aids in diesel fuels. A number of other kinds of lubricity additives are also known. Since the advent of low sulfur diesel fuels in the early 1990s, relatively large amounts of these lubricity additives have been used to provide a fuel that does not cause excessive wear of engine parts. Thus, it would be desirable if a way to reduce the amount of lubricity additives could be devised that would provide equivalent or superior performance of the fuels.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an object of the present invention to provide fuel lubricity compositions that improves lubricity over conventional additives.  
      It is another object of the present invention to provide fuel lubricity compositions that permit lower lubricity additive treatment levels while providing the equivalent lubricity performance.  
      In carrying out these and other objects of the invention, there is provided, in one form, a composition for improving the lubricity of diesel and kerosene distillate fuels having 0.2 wt % or less sulfur that has (a) at least one lubricity additive that can be an ester-based lubricity additive and/or an amide-based lubricity additive. Suitable ester-based lubricity additives include, but are not necessarily limited to reaction products of saturated, unsaturated, mixed saturated and unsaturated, mono-, di- and tri-carboxylic acids having from 12 to 72 carbon atoms with alcohols, glycols, polyglycols, and mixtures thereof. Suitable amide-based lubricity additives include, but are not necessarily limited to reaction products of saturated, unsaturated, mixed saturated and unsaturated and aryl substituted carboxylic acids having from 12 to 72 carbon atoms with amines selected from the group consisting of alkanolamines, alkylamines, cyclic amines, aromatic amines, polyamines, and mixtures thereof. The composition also includes (b) at least one second additive that may be a corrosion inhibitor and/or a stability additive. Suitable corrosion inhibitors include, but are not necessarily limited to saturated or unsaturated monomer, dimer, and trimer fatty acids, succinic acids, imidazolines, and mixtures thereof. Suitable stability additives include, but are not necessarily limited to hindered primary, secondary, and tertiary amines, amides, amine/aldehyde condensates, polymer dispersants, and mixtures thereof, where the stability additive is different from the lubricity additive. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      New compositions have been discovered which contain corrosion inhibitors and/or stability additives along with lubricity additives are useful as fuel lubricity aids, and which can offer the same fuel lubricity properties with reduced amounts of fuel lubricity additives. The use of the corrosion inhibitors and/or stability additives together with certain fuel lubricity additives creates a synergistic effect that permits reduced amounts of the fuel lubricity additives to be used, yet achieve comparable properties to compositions that do not contain the corrosion inhibitors and/or stability additives.  
      The invention relates to lubricity additive compositions for distillate fuels, as contrasted with products from resid. In the context of this invention, distillate fuels include, but are not necessarily limited to diesel fuel, kerosene, gasoline and the like. It will be appreciated that distillate fuels include blends of conventional hydrocarbons meant by these terms with oxygenates, e.g. alcohols, such as methanol, and other additives or blending components presently used in these distillate fuels, such as MTBE (methyl-tert-butyl ether), or that may be used in the future. In one non-limiting embodiment of the invention, the invention relates to low sulfur fuels, which are defined as having a sulfur content of 0.2% by weight or less, and in another non-limiting embodiment as having a sulfur content of about 0.0015 wt. % or less—such as the so-called “ultra low sulfur” fuels. Particularly preferred hydrocarbon fuels herein are diesel and kerosene.  
      Generally, in one embodiment of the invention the composition for improving the lubricity of distillate fuels is a mixture or blend of at least one first additive, that is a lubricity additive and at least one second additive. The lubricity additive may be either an ester-based lubricity additive or an amide-based lubricity additive or mixtures of both. Suitable ester-based lubricity additive include, but are not necessarily limited to reaction products of saturated, unsaturated, mixed saturated and unsaturated mono-, di- and tri-carboxylic acids having from 12 to 72 carbon atoms with alcohols, glycols, polyglycols, and mixtures thereof. These esters may be prepared by known techniques. Specific examples of suitable ester-based lubricity additives include, but are not necessarily limited to, a dimer fatty acid copolymer with ethyleneglycol-polyester, and glycerin monoleate, dioleate, and trioleate, and the like.  
      More specific examples of suitable saturated, unsaturated, mixed saturated and unsaturated mono-, di- and tri-carboxylic acids having from 12 to 72 carbon atoms suitable to prepare the ester-based lubricity additives of this invention include, but are not necessarily limited to, Arizona Unidyme 35 (unsaturated), Uniqema Pripol 1009 (saturated), oleic acid, stearic acid, and mixtures thereof. It should be understood that the definition of these suitable carboxylic acids include so-called synthetic acids, which may include, but are not necessarily limited to acids such as xylylstearic acid, phenylstearic acid, tolylstearic acid, ricinoleic acid, hydrogenated monomer and oligomer fatty acids, and aromatic substituted fatty acids and mixtures thereof. Further, more specific examples of suitable alcohols, glycols, and polyglycols (hydroxyl compounds) include, but are not necessarily limited to, ethylene glycol, propylene glycol, glycerol, C4 to C30 linear and branched alcohols, oxyalkylated linear and branched alcohols, and polyhydric alcohols prepared from oxyalkylation of alkylphenol formaldehyde resins and mixtures thereof. By the term “polyglycols” is meant polymers of glycols, where the polymer has 2 to 40 hydroxyl groups.  
      In another non-limiting embodiment of the invention, the ester lubricity additives may be polymeric, such as the dimer fatty acid copolymer with ethylene glycol lubricity additives described above or simple monomer acid esters (oleic, tallow, coco, etc.) made with glycols. It should also be understood that the lubricity additive esters of this invention include esters prepared by the condensation of a monomer fatty acid with triethanolamine to form an amino-substituted ester of the general structure: 
 
R—C(O)—OCH 2 CH 2 —N(CH 2 CH 2 OH) 2   (I) 
 
 where R=C12 to C 1-8  alkyl or alkenyl groups. 
 
      The suitable amide-based lubricity additives may include, but are not necessarily limited to reaction products of saturated, unsaturated, mixed saturated and unsaturated, and aryl substituted carboxylic acids having from 12 to 72 carbon atoms with amines selected from the group consisting of alkanolamines, alkyl-amines, cyclic amines, aromatic amines, and mixtures thereof. In one non-limiting embodiment of the invention, the amines have a generally low molecular weight, for instance from about 100 to about 500 weight average molecular weight. The saturated, unsaturated, mixed saturated and unsaturated, and aryl substituted carboxylic acids having from 12 to 72 carbon atoms used to make the amide-based lubricity additives may be the same carboxylic acids as those used in the preparation of the ester-based lubricity additives described above. More specific examples of suitable alkanolamines, alkylamines, cyclic amines, aromatic amines, etheramines, polyamines, and polyalkylene amines include, but are not necessarily limited to, diethanolamine, dibutanolamine, diisopropanolamine, diethylamine, cyclohexylamine, isopropylamine, hindered primary amines (e.g. Rohm &amp; Haas Primene 81 R and Primene RB3), and bis-N,N′-dibutylaminomethane and mixtures thereof. In one non-limiting embodiment of the invention, the amides should be hydroxy alkyl-substituted rather than just alkyl-substituted (that is alkanolamides rather than alkyl-amides). The processes and conditions used to make the amide-based lubricity additives are known to those of ordinary skill in the art. Specific examples of suit-able amide-based lubricity additives include, but are not necessarily limited to, alkanolamides of tall oil fatty acid, and the like.  
      As noted, the second additive may be a corrosion inhibitor or a stability additive. Suitable corrosion inhibitors include but are not necessarily limited to saturated or unsaturated monomer, dimer, and trimer fatty acids, succinic acids, imidazolines, and mixtures thereof. More particular examples of suitable corrosion inhibitors include, but are not necessarily limited to, dimer and trimer fatty acids that are the reaction products of C12-C22 saturated and unsaturated monomer acids to produce dimers and trimers, C12-C22 saturated and unsaturated monomer fatty acids and mixtures thereof, tetrapropenylsuccinic acid, and reaction products between C12-C22 saturated and unsaturated monomer fatty acids with blends of diethylenetriamine or aminoethylethanolamine.  
      The monomeric fatty acid components may be a saturated, monomeric fatty acid having from 12 to 22 carbon atoms, an unsaturated, monomeric fatty acid having from 12 to 22 carbon atoms, or a synthetic monomeric fatty acid having from 12 to 50 carbon atoms. In one general embodiment of the invention, a synthetic monomeric fatty acid is any monomeric fatty acid within the given carbon number range that does not occur in nature. In one non-limiting embodiment of the invention, a synthetic monomeric fatty acid is one that results from the modification of a natural fatty acid by a process including, but not limited to, alkylation, hydrogenation, arylation, isomerization or combinations of these modifications. In another, non-limiting embodiment of the invention, the synthetic monomeric fatty acid is formed by dimerizing any of the an unsaturated, monomeric fatty acids having from 12 to 22 carbon atoms mentioned above, and then hydrogenating them.  
      More specific examples of suitable saturated, monomeric fatty acids include, but are not limited to, lauric acid (dodecanoic acid); myristic acid (tetradecanoic acid); palmitic acid (hexadecanoic acid); stearic acid (octadecanoic acid); and the like. Specific examples of suitable unsaturated, monomeric fatty acids include, but are not limited to, oleic acid (cis-9-octadecenoic acid); tall oil fatty acid (e.g. Westvaco L-5); and the like. Specific examples of suitable synthetic, monomeric fatty acids include, but are not limited to, Union Camp Century 1105 and the like.  
      The oligomeric fatty acid components may be a saturated, oligomeric fatty acid having from 24 to 72 carbon atoms, or an unsaturated, monomeric fatty acid having from 24 to 72 carbon atoms. In one general embodiment of the invention, the oligomeric fatty acids may be made by dimerizing or trimerizing any of the unsaturated monomeric acids suitable for the monomeric fatty acid component described above.  
      Specific examples of suitable saturated, oligomeric fatty acids include, but are not limited to, dimer acid (e.g. Unichema Pripol 1009); and the like. Specific examples of suitable unsaturated, oligomeric fatty acids include, but are not limited to, dimer acid (e.g. Westvaco DTC-595); trimer acid (e.g. Westvaco DTC-195); and the like. In one embodiment of the invention it is preferred that the oligomeric fatty acid component be a dimer, although trimers are acceptable.  
      Suitable stability additives include antioxidants not necessarily limited to amines, amides, amine/aldehyde condensates, hindered primary amines (e.g. Rohm &amp; Haas Primene 81R) and hindered tertiary amines (e.g. dimethylcyclohexyl amine) and mixtures thereof, where the stability additive is different from the lubricity additive defined above. More particular examples of suitable stability additives include, but are not necessarily limited to, hindered C8-C22 primary, secondary, or tertiary amines, alkanolamides made from diethanolamine and fatty acids (such as those described above), condensates of C4-C12 alkyl phenols with aldehydes and alkyldiamines, and mixtures thereof. By “hindered C8-C22 primary amines” is meant primary amines that are sufficiently branched to provide at least some degree of steric hindrance. Suitable stability additives also include diaminomethanes, particularly bis-dialkyldiaminomethanes of U.S. Pat. No. 4,978,366, herein incorporated by reference.  
      In one non-limiting embodiment of the invention, the proportion of (a) lubricity additive in the total distillate fuel ranges from about 10 to about 200 ppm, whereas the proportion of the at least one (b) second additive ranges from about 1 to about 60 ppm. The proportions for the lubricity additive (a) are for the total amount of lubricity additives (a), should more than one type be used. It should be noted that the normal proportions of lubricity additives (a) typically range from as little as about 20 ppm to as much as 400 ppm. Thus, it may be seen that the lubricity additive (a) proportion may be reduced approximately in half using the synergistic composition of this invention, in one non-limiting embodiment thereof.  
      The proportions for the second additive (b) are for the total amount of second additives, should more than one type be used. In another non-limiting embodiment of the invention, the proportion of second component (b) in the distillate fuel ranges from about 10 to about 30 ppm.  
      It will be appreciated that the invention herein also encompasses distillate fuels containing the compositions of this invention as well as methods of improving the lubricity properties of distillate fuels using the compositions of this invention.  
      Typically, a solvent is preferably used in the compositions of the invention, where the solvent may be aromatic solvents and pure paraffinic solvents. Aromatic solvents are particularly preferred. The proportion of solvent in the total fuel lubricity aid composition may range from about 0 to 90 weight %. The use of a solvent is optional. Specific examples of suitable solvents include, but are not limited to paraffins and cycloparaffins, aromatic naphtha; kerosene; diesel; gasoline; xylene; toluene, alcohols; and the like.  
      Other, optional components of the distillate fuels of this invention in non-limiting embodiments may include, but are not necessarily limited to detergents, pour point depressants, cetane improvers, dehazers, cold operability additives, conductivity additives, biocides, dyes, and mixtures thereof. In another non-limiting embodiment of the invention, water is explicitly absent from the inventive composition.  
      The invention will be illustrated further with respect to the following non-limiting Examples that are included only to further illuminate the invention and not to restrict it.  
     EXAMPLES 1-3  
      Samples 1 through 3 were tested in the diesel fuels noted according to ASTM-6079 High Frequency Reciprocating Rig (HFRR) specifications at 60° C. The results are presented in Table I. Usually, a level of 450 μm or below is considered a “good” WSD value to have for a fuel, although some areas use a 460 μm level.  
               TABLE I                          WSD Results                                                 Lubricity   Dose,   Second   Dose,   WSD,       Ex.   Fuel   additive   ppm   additive   ppm   microns               1A   California   Additive A   100   —   —   576           ULSD       1B   California   Additive A    80   Additive B   20   302           ULSD       2A   California   Additive A   100   —   —   576           ULSD       2B   California   Additive A    80   Westvaco   20   490           ULSD           DTC-595       3A   European   Additive A   200   —   —   515           ULSD       3B   California   Additive A   180   Additive C   20   423           ULSD                  
 
      Definitions for Examples 1-3: 
      California ULSD An ultra low sulfur diesel fuel used as a standard in California.     European ULSD An ultra low sulfur diesel fuel used as a standard in Europe.     Additive A Alkanolamide lubricity additive available from Baker Petrolite.     Additive B Alkyl phenol/aldehyde polyamine stability additive available from Baker Petrolite.     Additive C Dimer fatty acid/alkyl succinic acid blend corrosion inhibitor available from Baker Petrolite.     DTC-595 Dimer fatty acid corrosion inhibitor available from Westvaco.    

      As can be seen in Table I, the wear scar data obtained using the inventive compositions of Examples 1B, 2B and 3B that contained stability additives or corrosion inhibitors was better than that obtained using conventional lubricity additives alone, even though the same total proportions of additives was used. These results demonstrate that there is a synergistic effect occurring that would allow less lubricity additive to be used when the second additive is present, to achieve the same WSD result.  
      In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been demonstrated as effective for improving the lubricity of fuels. However, it will be evident that various modifications and changes can be made thereto without departing from the broader spirit or scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific combinations of second additives (corrosion inhibitors and/or stability additives) falling within the claimed parameters, but not specifically identified or tried in a particular composition to improve the lubricity of fuels herein, are anticipated to be within the scope of this invention. It is anticipated that the compositions of this invention may also impart to the engines in which they are used as fuel lubricity aids, greater horsepower, lower emissions and better fuel economy as a result of less friction, whether they are used in diesel or gasoline engines.  
      It will be appreciated, of course, that the corrosion inhibitor additives of this invention will also have desirable corrosion-inhibiting properties in the ultimate distillate fuel. In turn, the stability additive will also have the ability to improve the stability of the distillate fuel, as well as the other beneficial properties of the invention herein.