Mineral oils: processes and products – Products and compositions
Reexamination Certificate
2001-10-19
2004-08-17
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Products and compositions
C208S015000, C208S017000, C585S001000, C585S006000, C585S016000
Reexamination Certificate
active
06776897
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a thermally stable distillate fuel blend comprising a highly paraffinic distillate fuel component, such as a product derived from the Fischer Tropsch process, and a petroleum-derived distillate fuel component having a high aromatic content and a process for making a stable blend when the components are antagonistic with respect to the other.
BACKGROUND OF THE INVENTION
Distillate fuels which are intended for use in internal combustion engines or jet turbines must meet certain minimum standards in order to be suitable for use. Diesel and jet fuel must have good oxidation stability in order to prevent the formation of unacceptable amounts of deposits which are harmful to the engines in which they are intended to be used. Distillates having very high levels of saturates, such as distillates recovered from the Fischer Tropsch process, have been shown to have excellent cetane numbers and low sulfur contents. Highly paraffinic distillates, as such, appear to be useful for blending with lower quality distillates, such as those with high aromatic contents, to obtain a distillate blend meeting the requirements for its intended application, whether as diesel fuel or jet fuel.
In general, two classes of oxidation stability are of concern in this disclosure. The first is the result of low sulfur levels in the distillate, such as found in Fischer Tropsch distillates and fuels which have been hydrotreated to low sulfur levels. Such hydrocarbons are known to form peroxides which are undesirable because they tend to attack the fuel system elastomers, such as are found in O-rings, hoses, etc. The second source of concern is in the formation of solid deposits as a result of the blending of the different components. For example, it has been found that highly paraffinic distillates, such as Fischer Tropsch products, when blended with highly aromatic petroleum-derived distillates, such as FCC light cycle oil, will result in an unstable blend which forms an unacceptable amount of solid deposits. When a blend of at least two distillate fuel components in some blending proportions result in the formation of unacceptable amounts of deposits as measured by ASTM D6468, the components are described as having “antagonistic properties”.
In the case of peroxide formation, it has been suggested that the formation of peroxides in the blends may be controlled by increasing the sulfur content of the blend. See WO 00/11116 and WO 00/11117 which describe the addition of at least 1 ppm sulfur to the blend in order to prevent sulfur formation. This approach has two drawbacks. The first is that this approach does not address the problem associated with the antagonistic properties of the blending components. The second problem is that sulfur in fuels is considered an environmental hazard and it is desirable to reduce the level of sulfur in fuels not increase it.
The present invention is directed to a process for blending highly paraffinic distillate fuel components and petroleum-derived distillate fuel components having high aromatics, the two components having antagonistic properties at certain ratios which result in the formation of unacceptable amounts of solid deposits. The process of the invention also may also be used to reduce the formation of peroxides in the blend without the addition of sulfur. The invention also results in a unique product blend which is suitable for use in internal combustion engines.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is directed to a distillate fuel blend useful as a fuel or as a blending component of a fuel suitable for use in an internal combustion engine, said distillate fuel blend comprising at least one highly paraffinic distillate fuel component having a paraffin content of not less than 70 percent by weight and at least one petroleum-derived distillate fuel component having an aromatic content of not less than 30 percent by weight, wherein the distillate fuel blend has an ASTM D6468 reflectance value of at least 65 percent when measured at 150° C. after 90 minutes. Highly paraffinic distillate fuel components are preferred which have paraffin contents of at least 80 percent by weight, with paraffin contents of more than 90 percent by weight being particularly preferred. Highly paraffinic distillate fuel components suitable for use in carrying out the present invention may be obtained from the oligomerization and hydrogenation of olefins, the hydrocracking of paraffins, or from the Fischer Tropsch process. Distillates recovered from the Fischer Tropsch process are especially preferred for use as the highly paraffinic blending component. The petroleum-derived distillate fuel component may be obtained from refining operations such as, for example, fluidized bed catalytic cracking (FCC and the related TCC process), coking, and pyroysis operations. In the case of the petroleum-derived distillate fuel component, those containing at least 40 percent by weight aromatics are preferred, with aromatic contents of 50 percent by weight or more being more preferred and 70 percent by weight or greater being even more preferred.
The distillate fuel blend composition described herein is suitable for use as a fuel in an internal combustion engine or it may be used as a distillate fuel blend component. As used in this disclosure the term “distillate fuel” refers to a fuel containing hydrocarbons having boiling points between approximately 60° F. and 1100° F. “Distillate” refers to fuels, blends, or components of blends generated from vaporized fractionation overhead streams. In general distillate fuels include naphtha, jet fuel, diesel fuel, kerosene, aviation gas, fuel oil, and blends thereof. A “distillate fuel blend component” refers to a composition which may be used with other components to form a salable distillate fuel meeting at least one of the specifications for naphtha, jet fuel, diesel fuel, kerosene, aviation gas, fuel oil, and blends thereof, especially salable diesel fuel or salable jet fuel, and most especially salable diesel fuel.
As used in this disclosure the term “salable diesel fuel” refers to material suitable for use in diesel engines and conforming to the current version of at least one of the following specifications:
ASTM D 975—“Standard Specification for Diesel Fuel Oils”
European Grade CEN 90
Japanese Fuel Standards JIS K 2204
The United States National Conference on Weights and Measures (NCWM) 1997 guidelines for premium diesel fuel
The United States Engine Manufacturers Association recommended guideline for premium diesel fuel (FQP-1A)
The term “salable jet fuel” refers to a material suitable for use in turbine engines for aircraft or other uses meeting the current version of at least one of the following specifications:
ASTM D1655-99.
DEF STAN 91-91/3 (DERD 2494), TURBINE FUEL, AVIATION, KEROSINE TYPE, JET A-1, NATO CODE: F-35.
International Air Transportation Association (IATA) “Guidance Material for Aviation Turbine Fuels Specifications”, 4th edition, March 2000
United States Military Jet fuel specifications MIL-DTL-5624 (for JP-4 and JP-5) and MIL-DTL-83133 (for JP-8).
The present invention is also directed to a process for preparing a stable distillate fuel blend comprising at least two components having antagonistic properties with respect to one another, said distillate fuel blend being useful as a fuel or as a blending component of a fuel suitable for use in an internal combustion engine which comprises the steps of (a) blending at least one highly paraffinic distillate fuel component having a paraffin content of not less than 70 percent by weight with at least one highly aromatic petroleum derived distillate fuel component; (b) determining the thermal stability of the blend of step (a) using a suitable standard analytical method; (c) modifying the blending of step (a) to achieve a pre-selected stability value as determined by the analytical method of step (b); and (d) recovering a distillate fuel blend that is characterized by having a reflectance value of at least 65 percent as
Bacha John D.
O'Rear Dennis J.
Burns Doane Swecker & Mathis L.L.P.
Chevron U.S.A.
Griffin Walter D.
Nguyen Tam M.
LandOfFree
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