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Fuel compositions

a technology of compositions and fuels, applied in the field of fuel compositions, can solve the problems of increasing the product of thermal instability reaction, high thermal stress of aviation fuels (kerosene fractions), and increasing the risk of instability reaction

Inactive Publication Date: 2008-10-09
SHELL OIL CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent text describes a method for formulating a fuel composition by blending together a non-Fischer-Tropsch derived base fuel and a Fischer-Tropsch derived fuel component, optionally with other fuel components. The resulting fuel composition has a JFTOT breakpoint of greater than 300°C. Additionally, the method results in a fuel composition with a peroxide level of 10 mg / kg or less after storage for 8 weeks at a temperature of at least 40°C. The technical effects of this patent text include improved fuel stability and reduced emissions.

Problems solved by technology

Aviation fuels (kerosene fractions) are subjected to high levels of thermal stress during use.
However, trends in modern engine design, to comply with ever tightening emissions legislation, may change this.
New common rail or unit injectors subject fuels to much more severe conditions than more traditional diesel engines, for example pressures of up to 2000 bar and temperatures above 100° C. Under these conditions, instability reactions are much more likely to occur.
Poor thermal stability in a fuel will result in an increase in the products of thermal instability reactions such as gums, lacquers and other insoluble components.
These in turn can block engine filters, foul fuel injectors and valves and hence be detrimental to engine efficiency and emissions control.
Fuel instability is also thought to lead to increased soot production in engine exhausts, which could lead to overloading of particulate traps.
It has also been seen, in the aviation industry, that thermal instability of a fuel can be exacerbated by the presence of trace catalytic metals—for example copper—which can occur if the fuel is able to dissolve such metals from the engine hardware, or from storage tanks or transportation equipment.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0112]This example assessed the ability of four different automotive diesel fuel compositions to solubilise catalytic metals when in contact with metal surfaces. The compositions were stored over a copper billet at 43° C. and atmospheric pressure, samples being taken monthly to determine their copper content by Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

[0113]The fuels used were:[0114]F1 a commercially available ultra low sulphur automotive diesel fuel (petroleum derived), sourced in the UK;[0115]F2& F3 commercially available zero sulphur automotive diesel fuels (petroleum derived), sourced in Sweden and Germany respectively; and[0116]F4 a Fischer-Tropsch derived gas oil (ex. Shell).

[0117]The four fuels had the properties listed in Table 1 below.

TABLE 1FuelpropertyTest methodF1F2F3F4CetaneASTM D61360.258.652.0>74.8numberDensity @IP 365 / 0.83120.81120.832 0.785215° C.ASTM(g / cm3)D4052KinematicIP 71 / 2.0412.86 3.606viscosity @ASTM D44540° C.(mm2 / s)Cloud pointIP 219−6−34−9.0 +2...

example 2

[0120]In this example, the intrinsic thermal stabilities of the four fuels F1 to F4 were assessed using the Jet Fuel Thermal Oxidation Tester (JFTOT), according to the standard test method ASTM D3241 (IP 323). This technique, developed for the evaluation of jet fuels, involves pumping fuel over a heated tube at a specified flow rate for a specified period of time. The JFTOT “breakpoint” is the highest temperature (measured to the nearest 5° C.) at which the fuel passes the JFTOT test criteria, which relate to tube appearance and test filter pressure differential. The JFTOT test was chosen as it subjects a fuel to higher temperatures than those typically observed in a diesel engine, and thus provides a relatively stringent assessment of a fuel's stability. It can also, being an accelerated test method, yield stability data in a relatively short time period.

[0121]The results for the four fuels are shown in Table 3.

TABLE 3JFTOTSulphurbreakpointFuel(mg / kg)(° C.)F139240F2350F3285F4>380

[0...

example 3

[0123]This example assessed the impact of copper pick-up on the thermal stability of diesel fuels. Fuels F2 to F4 (those having comparably low sulphur levels) were assessed using the JFTOT method as outlined in Example 1, after doping with an appropriate quantity of copper naphthenate. The doping levels were chosen in each case to approximate to those found in the fuels after 8 weeks' storage in contact with a copper billet, as observed in Example 2. Thus, 50 ppbw of copper was aimed for in fuels F2 and F3, this level being midway between the 80 ppbw and 30 ppbw that were respectively detected in these fuels at day 54. For the Fischer-Tropsch derived fuel F4, a dosing level of 20 ppbw was aimed for.

[0124]The JFTOT results are shown in Table 4.

TABLE 4CuCucontentcontentNeat fuelCu-doped(ppbw) -(ppbw) -JFTOTJFTOTSulphurtargetmeasuredbreakpointbreakpointFuel(mg / kg)levellevel(° C.)(° C.)F25055350345F35060285220F42015>380>380

[0125]As seen in Table 4, the Fischer-Tropsch derived fuel F4 st...

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Abstract

Use of a Fischer-Tropsch derived fuel component, in a fuel composition, is provided reducing the tendency of the composition to dissolve metals; increasing its thermal stability; reducing the concentration of a metal deactivator, antioxidant or detergent additive in the composition; or increasing the storage stability of the composition. The composition is preferably a diesel fuel composition.

Description

FIELD OF THE INVENTION[0001]The present invention relates to certain types of fuel compositions.BACKGROUND OF THE INVENTION[0002]The thermal stability of middle distillate fuels has traditionally been a cause for concern in the aviation industry. Aviation fuels (kerosene fractions) are subjected to high levels of thermal stress during use.[0003]For automotive diesel fuels, thermal stability has historically been less of a concern. However, trends in modern engine design, to comply with ever tightening emissions legislation, may change this. New common rail or unit injectors subject fuels to much more severe conditions than more traditional diesel engines, for example pressures of up to 2000 bar and temperatures above 100° C. Under these conditions, instability reactions are much more likely to occur.[0004]Fuel thermal instability reactions are recognised to result from a combination of hydrocarbon oxidation reactions and interactions between polar species present in the fuel. These ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C10L1/18
CPCC10L1/08C10L1/1625C10L10/02C10L10/04
Inventor ANSELL, CLAIRECLARK, RICHARD HUGHHEINS, RICHARD JOHNSMITH, JOHANNESTEPHENSON, TREVORWARDLE, ROBERT WILFRED MATTHEWS
Owner SHELL OIL CO