Abstract:
A method of increasing the conductivity of a hydrocarbon fuel comprising adding to the fuel an effective conductivity enhancing amount of one or more alkylphenol-formaldehyde resin alkoxylates.

Description:
TECHNICAL FIELD  
       [0001]     This invention is directed to methods of using alkylphenol-formaldehyde resin alkoxylates to enhance the electrical conductivity of hydrocarbon fuels, particularly low sulfur hydrocarbon fuels including diesel and jet fuel.  
       BACKGROUND OF THE INVENTION  
       [0002]     When fuels are moved at high flow rates in pipelines, transfer lines and hoses, static charge develops. Certain polar organic compounds present in fuel have the ability to dissipate this charge throughout the fuel matrix to minimize static charge build-up. Fuels having a sulfur content in the range of 5,000 ppm have the ability to naturally dissipate electrical build-up. Fuels with sulfur concentrations less than about 500 ppm do not have the ability to effectively dissipate electrical charge so static charge continues to build in fuel lines as the fuel continues to flow. Upon exiting the line, an electrical discharge and resulting spark can occur as the static charge contacts air and fuel vapors. In some cases, fuel vapors can ignite.  
         [0003]     Presently, sulfur-based organic compounds are used effectively as electrical conductivity improvers for fuels. These sulfur-based compounds are added to the fuel at various rates in order to ensure that the fuel possesses minimum conductivity values of 50 picosiemens (50 pS) or 50 mhos. Some jet fuels must meet a minimum conductivity specification of 200 pS.  
         [0004]     In June 2006, EPA regulations specifying a 15 ppm maximum sulfur limit for on-highway diesel fuel will take effect. Because of this rule, fuel refiners have requested sulfur-free additives of all types including electrical conductivity improvers.  
       SUMMARY OF THE INVENTION  
       [0005]     This invention is a method of increasing the conductivity of a hydrocarbon fuel comprising adding to the fuel an effective conductivity enhancing amount of one or more alkylphenol-formaldehyde resin alkoxylates.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0006]     “Alkylphenol-formaldehyde resin alkoxylate” means the reaction product of one or more alkylphenol-formaldehyde resins as described herein with about 15 to about 95 weight percent, based on alkylphenol-formaldehyde resin of ethylene oxide and/or propylene oxide under heat and pressure in the presence of an acid, base or metallic catalyst. A preferred catalyst is potassium hydroxide. Preferably the reaction is conducted at a temperature of about 120° C. to about 180° C. and a pressure of about 80 psi. The reaction may be conducted neat or in a suitable solvent such as xylene, toluene, light or heavy aromatic naphtha, and the like.  
         [0007]     In cases where the alkylphenol-formaldehyde resin is reacted with both ethylene oxide and propylene oxide, the ethylene oxide and propylene oxide may be added in random or block fashion.  
         [0008]     Random addition of ethylene oxide and propylene oxide involves both components being added to the resin simultaneously, such that the rate of addition to the resin is controlled by their relative amounts and reaction rates. An alkoxylate prepared by random addition of ethylene oxide and propylene oxide or by addition of a mixture of propylene oxide and ethylene oxide is referred to herein as a “mixed copolymer”.  
         [0009]     In the case of block addition, either the ethylene oxide or propylene oxide is added first to the resin and allowed to react. The other component is then added and allowed to react. An alkoxylate prepared by block addition of ethylene oxide and propylene oxide is referred to herein as a “block copolymer”.  
         [0010]     Alkylphenol-formaldehyde resins are typically prepared by the acid or base catalyzed condensation of an alkylphenol with formaldehyde. Alkyl groups are straight or branched and contain about 3 to about 18, preferably about 4 to about 12 carbon atoms.  
         [0011]     Representative acid catalysts include dodecylbenzenesulfonic acid (DDBSA), toluene sulfonic acid, boron trifluoride, oxalic acid, and the like. Representative base catalysts include potassium hydroxide, sodium methoxide, sodium hydroxide, and the like.  
         [0012]     Alkylphenol-formaldehyde resins are well known intermediates used in making alkylphenol-formaldehyde alkoxylate emulsion breakers. They are routinely manufactured by a number of companies including Nalco Energy Services, Sugar Land, Tex. and Uniqema, a division of ICI, Cleveland, England.  
         [0013]     In an embodiment, the alkylphenol-formaldehyde resin alkoxylates are prepared by alkoxylation of alkylphenol-formaldehyde resin having a weight average molecular weight of about 500 to about 5,000.  
         [0014]     In an embodiment, the alkylphenol-formaldehyde resin alkoxylates are prepared by alkoxylation of the alkylphenol-formaldehyde resin with about 15 to about 75 weight percent of ethylene oxide, propylene oxide, or a mixture thereof.  
         [0015]     In an embodiment, the alkylphenol-formaldehyde resin alkoxylates are prepared by alkoxylation of alkylphenol-formaldehyde resin having a weight average molecular weight of about 1,500 to about 4,000.  
         [0016]     In an embodiment, the alkylphenol-formaldehyde resin alkoxylates are selected from the group consisting of nonylphenol-formaldehyde resin alkoxylate, butylphenol-formaldehyde resin alkoxylate and amylphenol-formaldehyde resin alkoxylate, or a mixture thereof.  
         [0017]     In an embodiment, the alkylphenol-formaldehyde resin alkoxylate is nonylphenol-formaldehyde resin alkoxylate.  
         [0018]     In an embodiment, the alkylphenol-formaldehyde resin alkoxylate is nonylphenol-formaldehyde resin ethoxylate.  
         [0019]     In an embodiment, the nonylphenol-formaldehyde resin ethoxylate is prepared by alkoxylation of nonylphenol-formaldehyde resin having a weight average molecular weight of about 2100 to about 2700 with about 33 to about 66 weight percent, based on nonylphenol-formaldehyde resin, of ethylene oxide.  
         [0020]     In an embodiment, about 25 ppm to about 125 ppm of the alkylphenol-formaldehyde resin alkoxylates are added to the fuel.  
         [0021]     In an embodiment, the fuel is selected from the group consisting of diesel fuel, jet fuel, kerosene, fuel oil, light gas oil, heavy gas oil, light cycle gas oil, heavy cycle gas oil and vacuum gas oil.  
         [0022]     In an embodiment, the fuel is diesel fuel.  
         [0023]     In an embodiment, the diesel fuel has a maximum sulfur content of less than about 15 ppm.  
         [0024]     In an embodiment, the fuel has a minimum conductivity value of about 50 pS.  
         [0025]     In an embodiment, the fuel has a minimum conductivity value of about 200 pS.  
         [0026]     In an embodiment, the fuel is jet fuel.  
         [0027]     In an embodiment, the diesel fuel is selected from #2 high sulfur diesel fuel and #2 low sulfur diesel fuel.  
         [0028]     In addition to the alkylphenol-formaldehyde resin alkoxylates of the invention, other additives known in art can be added to the fuel. Such additives may include anti-knock agents such as tetraalkyl lead compounds, lead scavengers such as haloalkanes (example ethylene dichloride and ethylene dibromide), deposit preventers or modifiers such as triaryl phosphates, dyes cetane improvers, antioxidants, rust inhibitors such as alkylated succinic acids and anhydrides, bacteriostatic agents, gum inhibitors, metal deactivators, upper cylinder lubricants, anti-icing agents and the like. In addition, in certain applications the composition of the present invention can include an ash dispersant. Such ash dispersants are preferably esters of mono or polyol and a higher molecular weight mono or polycarboxylic acid acrylating agent containing at least 30 carbon atoms.  
         [0029]     The foregoing may be better understood by reference to the following examples, which are presented for purposes of illustration and are not intended to limit the scope of this invention.  
       EXAMPLE 1  
       [0000]     Preparation of a Nonylphenol-formaldehyde Resin.  
         [0030]     Into a stainless steel high temperature/low pressure reactor is charged 4-nonylphenol (63.3 g), alkylsulfonic acid (0.3 g) and 65.5° C. flash point aromatic solvent (16.0 g). The agitator is started and the reaction mixture is heated to 100° C. and held for 20 minutes. The reaction mixture is then cooled to 65° C., purged with nitrogen and further cooled to 50° C. Paraformaldehyde (2.9 g) and oxalic acid (71.5% aqueous solution, 0.36 g) are added into the reactor. When the exothermic reaction reaches a temperature of about 67° C. cooling is initiated in order to maintain reaction temperature below about 99° C. When the reaction temperature drops to about 77° C., cooling is stopped and paraformaldehyde (5.8 g) is added with additional cooling if necessary. The reactor is vented and the reaction temperature is increased to about 88° C. and maintained for about 4 hours. The reactor is then cooled and the product is removed.  
       EXAMPLE 2  
       [0000]     Preparation of a Nonylphenol-formaldehyde Resin Alkoxylate.  
         [0031]     Into a high pressure stainless steel reaction vessel is charged 4-nonylphenol-formaldehyde resin (62.56 g), prepared as in Example 1. Stirring is initiated and KOH (0.44 g) is added. The reactor lid is sealed and the vessel is heated to about 110° C. at a pressure of about 600 mm Hg for about 15 minutes. Ethylene oxide is added in 3.0 g, 11.0 g and 23 g portions over periods of 30, 90 and 90 minutes, respectively, while maintaining the reaction vessel at a temperature below about 177° C. and a pressure below about 4.9 atmospheres. The reaction mixture is held until the pressure stabilizes. The reaction vessel is then cooled and the title product is removed.  
       EXAMPLE 3  
       [0000]     Conductivity Testing.  
         [0032]     Conductivity testing is conducted pursuant to test method ASTM D02624 Standard Test Method for Electrical Conductivity of Aviation and Distillate Fuels. The results are shown in Table 1.  
                                                                   TABLE 1                           Conductivity Testing                    Dosage   Conductivity   Conductivity   Conductivity       Fuel   Additive   (ppm)   pS   pS (5 days)   pS (9 days)                    Ultra   None   —   88   73   58       low       sulfur       diesel       Ultra   A 1     10   358   351   332       low       sulfur       diesel                   1 Nonylphenol-formaldehyde resin alkoxylate prepared according to the method of Example 2.             
 
         [0033]     As shown in Table 1, representative alkylphenol-formaldehyde resin alkoxylates effectively increase the conductivity of low sulfur fuels at low treat rates. Accordingly, the additives described herein can be used to restore the electrical conductivity properties lost during the severe hydroprocessing used to prepare low sulfur fuels.  
         [0034]     Changes can be made in the composition, operation and arrangement of the method of the present invention described herein without departing from the concept and scope of the invention as defined in the following claims: