Abstract:
A fuel additive package is disclosed that prevents degradation of hydrocarbon fuels upon storage and permits extended use of such motor fuels without intake-valve deposit formation in vehicle motors. The additive contains an antioxidant, metal deactivator, corrosion inhibitor, and detergent. The corrosion inhibitor, preferably a carboxylic acid containing a carbon number equal to or less than 18 and the detergent component, preferably a polyisobutylene diamine are selected to avoid antagonistic effects with the antioxidant and metal deactivator components while the antioxidant and metal deactivator components are used in markedly reduced amounts to avoid antagonistic effects resulting in increased intake-valve deposits.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to additives for hydrocarbon fuels. In one aspect it relates to additives for hydrocarbon fuels which minimize the degradation of the hydrocarbon fuels upon storage and permit extended use of such motor fuels in vehicles without deposit formation. In another aspect it relates to additive-containing hydrocarbon fuels which maintain their stability during long-term storage of the fuels and can be used in vehicles without undesirable intake-valve deposit formation.  
         BACKGROUND OF THE INVENTION  
         [0002]    After new automobiles, trucks and motor vehicles, in general, are assembled, their fuel tanks are generally filled to some extent with an appropriate fuel before the vehicles are shipped to their point of sale and delivery to the ultimate customer. Because of the global nature of the motor vehicle industry, with the assembly of the vehicles often times taking place in a different part of the world relative to the point of sale of the vehicle, the fuel that is placed in these fuel tanks often stands unused for extended periods of time during shipment and storage of the vehicles. During these periods of time, the fuel in the fuel tanks, now effectively being in storage, must retain its initial integrity and not degrade with the degradation exhibiting itself through subsequent starting and running problems in the new vehicle and also by the formation of undesirable deposits in the fuel systems of the vehicles leading to longer term operability problems. The fuel so used must resist gum and sediment formation, minimize oxidation and prevent corrosion in the metallic portions of the fuel system as well as passivate fresh metal surfaces. Likewise, the fuel storage facilities, for example, tankage, pumps and plumbing, at the motor vehicle assembly site are also susceptible to the deposition of these unwanted solid materials from the quantities of stored motor fuels awaiting transfer to the newly assembled vehicles.  
           [0003]    The desired stability of the fuel is usually attained through the addition of appropriate additives to the fresh fuel. Typically, complex combinations of antioxidants, such as aromatic diamines or hindered phenols, carboxylic acid-based corrosion inhibitors, and metallic ion sequesterants such as salicylidene diamines are added as a stability-inducing package to the fuel. The term “package” is used typically to indicate the complex combination of the various stability-inducing materials often times diluted with a solvent or solvents compatible with the various individual additive materials and the fuel to be treated. This package is generally prepared as a separate entity prior to its addition to the fuel.  
           [0004]    If such a stability-inducing additive package is not employed, spontaneous deposition of undesirable deposits of solid, insoluble materials often occurs in the fuel tanks and systems of the new vehicles. These deposits, also referred to as gum, are mainly formed from oxidized and/or polymerized hydrocarbons. If a stability-inducing additive package is employed, gum formation in new vehicles can be reduced or eliminated.  
           [0005]    U.S. Pat. No. 6,083,288 (Wolf) discloses such a fuel additive wherein the most-preferred embodiment of the stability-enhancing package disclosed in Wolf is summarized as follows:  
                                                                 COMPONENT   WEIGHT PERCENTAGE                                        N,N′-di-sec-butyl-p-   7.3           phenylene diamine           2,6-di-t-butyl phenol   2.8           other phenols   0.9           N,N′-bis-salicylidene-1,2-   9.8           propane diamine           Amine O Registered TM   5.2           Xylene   44.0           2-propanol   30.0           TOTAL   100.0                      
 
           [0006]    In this connection, the EPA in accordance with the EPA&#39;s 1997 Final Regulation LAC for gasoline detergents requires a detergent additive to prevent fuel injector fouling and intake-valve deposits. If the stability-inducing additive package interacts antagonistically with the detergent, undesirable intake-valve deposits can form. Generally because only a limited amount of factory-fill gasoline is used, the antagonistic effect is not a concern. However if the factory-fill gasoline is used for an extended period of time, unacceptable amounts of deposit can form. The present invention permits the extended use of factory-fill gasoline achieved by careful selection of both the stability additives and detergent additives to avoid the antagonistic effect between stability additives and detergent additives. In particular the present invention will permit drivers to use factory-fill gasoline for mileage accumulation and pool cars in addition to the typical newly manufactured vehicle initial fill use.  
         SUMMARY OF THE INVENTION  
         [0007]    One object of the present invention is to provide a stability-enhancing additive which can be added to a hydrocarbon fuel and which minimizes solid deposit and gum formation upon storage of the fuel and permits the use of such fuel in vehicles without undesirable intake-valve deposition in the vehicles. A still further object of the invention is to provide a hydrocarbon fuel with enhanced stability toward oxidation and solid deposit formation during storage while concomitantly permitting extended driving of vehicles using such fuel without intake-valve deposits. These objects will be attainable through the use of the invention as described below.  
           [0008]    This invention also uses a combination of aromatic amine and hindered phenols, and in a preferred embodiment a mixture of N,N′-dialkyl-p-phenylene diamine and butylated phenols as stabilizers toward hydrocarbon oxidation. However such antioxidants are used in markedly reduced amounts compared to the prior art factory fill fuel. This combination provides for good oxidative stability for virtually all types of hydrocarbon fuels.  
           [0009]    In addition, this invention in contradistinction to the prior art includes a substantially reduced amount of a standard type of metal deactivator, typically alkane diamine, preferably a salicylidene diamine, to passivate fresh metal surfaces of the fuel storage vessels and tanks, and the fuel transfer apparatus and to sequester oxidation-promoting metal ions which may be in the fuel. It has been found that the subject metal deactivator relatively greater amounts caused intake valve deposits.  
           [0010]    Additionally, the present invention includes an intake-valve detergent that is not antagonistic vis-à-vis the stability additives. The detergents used in accordance with the present invention are selected from the group consisting of polyalkylene diamine and polyoxyalkylene diamine.  
           [0011]    The present invention also includes the use of a corrosion inhibitor that has been found not to have an antagonistic effect in contradistinction to the prior use of imizolines. Specifically the present invention involves the substitution of the imizolines with carboxylic acids. The detergents used in accordance with the present invention are selected from the group consisting of polyalkylene diamine and polyoxyalkylene diamine. More particularly, the carboxylic acids used in the present invention have carbon numbers of 18 or less and may be mono or polycarboxylic acids.  
           [0012]    The present invention employs an aromatic solvent to solubilize the components of the additive package and to facilitate the handling and addition of the additive package in concentrations convenient and appropriate for addition to the hydrocarbon fuel. Other solvents of mixtures such as alcohols are suitable for use in the present invention.  
           [0013]    Additionally, this invention includes a fuel composition, typically, but not limited to, a motor gasoline, to which the additive package comprising the above described components has been added and which exhibits enhanced stability, especially toward solid deposit formation, during storage while concomitantly permitting extended mileage without causing excessive intake-valve deposits.  
         DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
         [0014]    Fuel stabilization additive packages are typically utilized by adding an amount of the package to fresh fuel such that the resulting fuel shows no deleterious stability problems over a time period at least as long as the anticipated storage period. Thus, the fuel stabilization package of the present invention is added to fresh fuel, typically, motor gasoline, at the rate of from 0.25 gallon to 1.0 gallon of additive package per 1000 gallons of the fresh fuel. In this invention, a preferred blending ratio is 0.5 gallon of the additive package per 1000 gallons of the fresh fuel.  
           [0015]    The fuel additive package of this invention comprises a combination of stability-enhancing active ingredients added to inert carrier ingredients. Typically, the concentration of the active ingredients ranges from 13 weight percent to 78 weight percent of the final additive package composition with the inert carrier components concentration ranging from 87 weight percent to 22 weight percent, respectively. Preferably, the active ingredients represent 26 weight percent of the additive package with the inert carrier components representing the remaining 74 weight percent.  
           [0016]    The inert components of the additive package comprise a mixture of aromatic hydrocarbons and optionally alcoholic solvents that effectively solubilize the stability-enhancing active components of the package while at the same time exhibit high solubility in the fuel to be treated. Constraints of cost, compatibility with combustion processes, purity and their own long-term stabilities must be considered when choosing the inert carrier components. It has been found that mixtures of the various isomers of xylene can function as one inert component while a simple aliphatic alcohol, namely 2-propanol, often referred to as isopropanol, can function as another inert ingredient.  
           [0017]    In addition to the inert carrier component, the stability-inducing additive package typically contains active components of four different compound classes, namely, antioxidants, metal deactivators (often referred to as metal ion sequesterants) corrosion inhibitors, and deposit control additives or detergents.  
           [0018]    This invention uses a combination of aromatic amines and hindered phenols and in a preferred embodiment a combination of N,N′-dialkyl-p-phenylene diamine and poly-butylated phenols to provide the antioxidant functionality in the stability-inducing additive package. This combination has been found to provide good oxidation stability for virtually all hydrocarbon fuels, including motor gasoline. The preferred oxidation stabilizers have been determined to be N,N′-di-sec-butyl-p-phenylene diamine and 2,6-di-t-butyl phenol. Lesser amounts of other isomers of the 2,6-di-t-butyl phenol can also be present without impeding the efficacy of the components. The stability-inducing additive package typically contains 5.5 to 3.0 weight percent of the aromatic amine or more preferably N,N′-di-sec-butyl-p-phenylene diamine and 2.7 to 1.2 weight percent of the hindered phenols and more particularly butylated phenols. The preferred composition of the stability-inducing additive package contains 4.1 weight percent N,N′-di-sec-butyl-p-phenylene diamine and 1.5 weight percent 2,6-di-t-butyl phenol with 0.5 weight percent other isomers of this phenol. These amounts are markedly reduced from the prior art quantities.  
           [0019]    The metal inactivation (metal ion sequestering) functionality of the stability-inducing additive package of the present invention is provided by an alkane amine or more preferably N,N′-bis-salicyclidene-1,2-propane diamine. However, due to the discovery of the antagonistic effect, this metal inactivation compound is also present in substantially reduced amounts. Typically this component can be utilized in the practice of this invention in the 1.5 to 0.05 weight percent range. Preferably, this component is utilized at the 0.68 weight percentage level in the additive package to be added to a fuel.  
           [0020]    The corrosion inhibitor additive found to reduce intake-valve deposition in contradistinction to the use of imidazoline substituted amidines is a carboxylic acid having a carbon number of 18 or less. These acids include mono or polycarboxylic acids, with dodecenyl succinic acid being the most preferred acid. Typically, this component can be utilized in the practice of this invention in the 5.0 to 0.5 weight percent range. Preferably, this component is utilized at the 3.0 weight percentage level.  
           [0021]    Without wishing to be bound by theory, it is believed that the imidazoline has an antagonistic on the deposit control additive. Specifically, the imidazoline reacts with acidic sites on the valve deposit thereby blocking the deposit control additive amine and not permitting dissolution. Further, the imidazoline contributes to the mass of the deposits.  
           [0022]    The detergent additive that provides the desired low intake-valve deposition is selected from the group consisting of polyalkylene diamine and polyoxyalkylene diamine.  
           [0023]    In a preferred embodiment, the detergents of the present invention may be:  
           [0024]    Polyisobutylene amine: A—(C 4 H 8 ) n —X—NHR n=7 to 100, R═H or A—(C 4 H 8 ) n —X, A and X are small groups (H or lower alkyl or branched alkyl or aryl) that may contain heteroatoms (O, N, S) to facilitate linking or initiation; or  
           [0025]    Polyisobutylene diamine: A—(C 4 H 8 ) n —X—NH—CH 2 CHA—NHR, n=7 to 100, R, A, X as defined above; or  
           [0026]    Polyether amine: R(CH 2 CHR′—O) n —X—NH 2 ; n=2 to 100; R═R″ C 6 H 4 —O, R″═C8 to 24 hydrocarbyl; R′═H, CH 3 , C 2 H 5 ; X as defined above, with the diamine being the most preferred.  
           [0027]    Typically, this component can be utilized in the practice of this invention in the 15 to 70 weight percent range. Preferably, this component is utilized at the 36.4 weight percent level.  
           [0028]    The most-preferred embodiment of the stability-enhancing package of this invention is summarized as follows:  
                                                                 COMPONENT   WEIGHT PERCENTAGE                                        N,N′-di-sec-butyl-p-   4.1           phenylene diamine           2,6-di-t-butyl phenol   1.5           other phenols   0.5           N,N′-bis-salicylidene-1,2-   0.68           propane diamine           Dodecenyl succinic acid   3.0           Polyisobutylene diamine detergent   36.4           Mixed Xylene   53.72           Demulsifier   0.1           TOTAL                      
 
           [0029]    This mixture is added to commercial gasoline at the rate of 0.5 gallons per 1000 gallons of gasoline to give a highly stabilized gasoline. The additive can be used with the low sulfur containing fuels, ethanol containing fuels, and reformulated gasoline such as Phase II gasoline. More particularly, the motor fuel can be gasoline containing ethanol or other oxygenates such that the oxygen content is in the range of 0.4 to 5 weight percent or more. Additionally, the motor fuel can be gasoline containing less than 100 ppmw, less than 80 ppmw, less than 50 ppmw or less than 30 ppmw sulfur. Further, the motor fuel can be a gasoline that contains oxygen in the range of 0.4 to 5 weight percent or more and has less than 100 ppmw sulfur. 
       
    
    
     EXAMPLE  
       [0030]    The present example shows how the additive formulation in accordance with the present invention provides superior intake valve deposit performance over the prior art additive packages and other comparative additive packages.  
         [0031]    Engine Intake Valve Deposit Tests, “IVD tests” were run essentially according to ASTM D 6201-97, “Standard Test Method for Dynamometer Evaluation of Unleaded Spark-Ignition Engine Fuel for Intake Valve Deposit Formation”. These tests were carried out on regular unleaded fuels containing additives in accordance with the present invention and fuels containing comparative additives. Briefly, this test uses a 1994 Ford 2.3 L in-line, four cylinder engine connected to a dynamometer. The engine is built to rigid specifications using new, weighed intake valves. A rigorous quality control procedure is used to verify operation and key parameters are monitored during the test period to ensure repeatability of the procedure. The fuel system is flushed and filled with new test fuel. The engine is operated at two modes, the first being 2000 rpm and 230 mm Hg manifold absolute pressure for 4 minutes and the second being 2800 rpm at 540 mm Hg manifold absolute pressure for 8 minutes. There is a 30 second ramp between the stages. The two stages are repeated until 100 hours testing time elapses. After the test time, the intake valves are removed and weighed to determine the amount of deposit formed. Initial testing indicated that relatively good correlation of intake valve deposits between shorter testing time (24 hours) and the standard 100 hours test could be obtained. Therefore, for some tests, the procedure was modified to stop the test after 24 hours and extrapolate (i.e., multiply by 4) the deposits to 100 hours so that all tests could be compared on the same basis.  
         [0032]    The fuels used in the present example were treated at the level of 0.5 gallons additive per 1000 gallons gasoline.  
         [0033]    Table I sets out the trade names, applications, and commercial sources for the various components used in the comparative and invention additives.  
                       Table I                       Component Material   Function   Trade Name and Source                   N,N′-di-sec-butyl   Antioxidant   AO-22, Octel-Starreon       phenylene diamine       2,6-di-t-butyl phenol +   Antioxidant   AO-37 (75% 2,6-di-t-butyl       other phenols       phenol, 25% other               butylated phenols), Octel-               Starreon       N,N′-bis-salicylidene-   Metal Deactivator   DMD (75% active, in       1,2-propane diamine       xylene), Octel-Starreon       Xylene   solvent       2-Propanol   solvent       polyisobutylene amine   detergent   PURADD AP-2000, BASF       polyether amine   detergent   OGA-492, Oronite       polyisobutylene   detergent   DMA-548, Octel-Starreon       diamine       mixed dimer acids   corrosion inhibitor   DCI-6A, Octel-Starreon       dodecenyl succinic   corrosion inhibitor   DDSA free acid (75%       acid       active, in xylene)       2-(8-hepthldecenyl)-4,   corrosion inhibitor   Amine O, CIBA       5-dihydro-1H-       imidazol-       1-ethanol       Tolad 9308 (dehazer)   Dehazer/Demulsifier   TOLAD 9308, Baker               Petrolite                  
 
         [0034]    [0034]                                                                                                           Table II                           Equivalent Compositions at 100% of Indicated Chemical Species                X-                                               Fluid       Material   M2   #3   #4   #10   #11   #12   #13   #14   #15   #16                    N,N′di-sec-butyl   7.3   6.8   6.8   6.8   6.8   6.8   6.8   3.4   3.4   4.1       phenylene       diamine       2,6-di-t-butyl   3.7   3.4   3.4   3.4   3.4   3.4   3.4   1.7   1.7   2       phenol + other       phenols       N,N′-bis-   9.8   6.825   6.825       6.825       6.825       1.2   0.675       salicylidene-1,2-       propane diamine       Xylene   44   37.875   29.675   59.4   52.575   55.4   48.575   64.5   60.3   53.725       2-Propanol   30   20   20       polyisobutylene r   2.       amine       polyisobutylene       22.2   30.3   30.3   30.3   30.3   30.3   30.3   30.3   36.4       diamine       mixed dimer       1.6   1.6           4   4       acids       dodecenyl                                   3   3       succinic acid       2-(8-   5.2   1.3   1.3       hepthldecenyl)-       4,5-dihydro-1H-       imidazole-1-       ethanol       Tolad 9308           0.1   0.1   0.1   0.1   0.1   0.1   0.1   0.1       (dehazer)       TEST       Mod. Nace 1                 E   D   B   B+       A   A       IVD Test Time,   10   100   24   24   24   24   24   24   24   24       hr,       Avg. IVD   141.25   918.75   137.75   15   50.8   23.8   45   11.5   30.2   10.25       100 hr IVD   1412.5   918.75   573.96   62.5   211.17   99.2   187.5   47.9   125.8   42.7       ASTM D525               &gt;1440                   &gt;1440   &gt;1440       Oxidation       Stability                                    
         [0035]    An inspection of Table II clearly shows that Comparative Additives M2, 3 and 4 containing imidazole show markedly greater intake-valve deposits than Additives 15 and 16 in accordance with the present invention.  
         [0036]    Comparative Additive 11 versus Comparative Additive 10 shows that the presence of metal deactivator in a relatively great amount has a deleterious effect on intake-valve deposits. Comparative Additive 12 versus Comparative Additive 10 shows that the corrosion inhibitor has a detrimental effect on intake-valve deposits while improving the NACE corrosion valves.  
         [0037]    Comparative Additive 12 versus Comparative Additive 13 shows that the effect of metal deactivator is detrimental to intake-valve deposits; however, both show improved NACE corrosion valves due to the presence of the corrosion inhibitor.  
         [0038]    Comparative Additive 14 versus Comparative Additive 10 shows directionally improvement in intake-valve deposits when the amount of antioxidant is reduced as required by the present invention.  
         [0039]    Invention Additive 15 versus Comparative Addition 13 shows improved intake-valve deposits by virtue of using a lower level of metal deactivator, a lower level of antioxidants and a lower molecular weight (i.e., lower carbon number) corrosion inhibitor in accordance with the process of the invention.  
         [0040]    Invention Additive 16 versus Comparative Additive 12 shows the improved effect on intake-valve deposits by a lower molecular weight corrosion inhibitor while including a lower level of metal deactivator, which also provides good corrosion protection.  
         [0041]    Finally, Invention Additives 15 and 16 show equivalent oxidation results to Comparative Additive 10, despite the larger amount of antioxidants present in Additive 10.  
         [0042]    When the Invention Additive Package 16 as set forth in Table II was used with a national generic certification fuel containing 10% ethanol and no ethanol, the 100 hr intake-valve deposits, avg. mg. were 31.8 and 31 respectively. This showed that the additive in accordance with the present invention afforded the beneficial intake valve deposit results in a fuel containing ethanol.