| Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products -> Monitor Keywords |
|
|
 
Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch productsRelated Patent Categories: Mineral Oils: Processes And Products, Products And Compositions, FuelsStable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070187292, Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] The present application is a continuation-in-part of U.S. application Ser. No. 09/999,667, "Distillate Fuel Blends from Fischer Tropsch Products with Improved Seal Swell Properties," filed Oct. 19, 2001, the contents of which are hereby incorporated by reference. The present application is also related to U.S. patent application Ser. No. ______(Docket No. 005950-779) entitled "Highly Paraffinic, Moderately Aromatic Distillate Fuel Blend Stocks Prepared by Low Pressure Hydroprocessing of Fischer Tropsch Products," filed herewith. FIELD OF THE INVENTION [0002] The invention is directed to a low sulfur distillate fuels comprising a Fischer-Tropsch distillate fuel blend stock, which have excellent stability and moderate content of unsaturates. BACKGROUND OF THE INVENTION [0003] Distillate fuel derived from the Fischer-Tropsch process is highly paraffinic and has excellent burning properties and very low sulfur. This makes Fischer-Tropsch products ideally suited for fuel use where environmental concerns are important. Fuels with good or preferably excellent stabilities are always desired, and stable fuels can be produced by hydrotreating or hydrocracking Fischer Tropsch products. However, conventional hydrotreating and hydrocracking processes require the use of expensive hydrogen to saturate olefins and convert oxygenates into paraffins. [0004] Stable diesel fuels with low sulfur contents and high cetane indexes, are desired because of their low emissions and good engine performance. Likewise stable jet fuels with low sulfur contents and high smoke points are desired. Fuels of this type can be prepared from Fischer-Tropsch products. The preparation of distillate fuels from Fischer Tropsch processes is well known. [0005] While they are highly paraffinic, Fischer-Tropsch products also contain olefins, alcohols, and traces of other compounds that can cause problems with stability. Typically, hydroprocessing is used to saturate essentially all the olefins and remove oxygenates. However, hydroprocessing requires the use of expensive hydrogen gas and expensive facilities designed to operate at high pressure. [0006] ASTM specifications for Diesel Fuel (D985) describe stability measurements for the respective fuels. For diesel fuel, ASTM D6468, "Standard Test Method for High Temperature Stability of Distillate Fuels" is under consideration as a standard test method for a diesel fuel and this test can provide a good measure of the stability of the fuel. Neat hydrotreated and hydrocracked Fisher Tropsch products typically have excellent stabilities in this test. ASTM specifications for Jet Fuel A and A-1 (D1655) describe the use of the JFTOT test ASTM D3241 with a pass at 260.degree. C. Higher stabilities are often desired. For example, Colonial Pipeline's Quality Assurance guidelines from February 2003 (section 3.19.1 on page 3B-33) require fungible aviation kerosene to have a JFTOT stability of 275.degree. C. or greater. This higher stability requirement will provide some compensation for degradation in the stability of the product during shipping. The Coordinating Research Council's Handbook of Aviation Fuel Properties, Third Printing, May 1988 describes on page 102 (Table 10) that several military jet fuels have higher stability requirements than commercial Jet A: JP-9 and JP-10 require a stability of 300.degree. C. or greater, JP-7 and TS require a stability of 335.degree. or greater. Highly stable jet fuels are in general desirable. [0007] In addition to conventional measurements of stability (thennal and storage), studies by Vardi et al (J. Vardi and B. J. Kraus, "Peroxide Formation in Low Sulfur Automotive Diesel Fuels," February 1992, SAE Paper 920826) describe how fuels can develop significant levels of peroxide during storage, and how these peroxides can attack fuel system elastomers (O-rings, hoses, etc.). The formation of peroxides can be measured by Infrared spectroscopy, chemical methods, or by the attack on elastomer samples. As described by Vardi et al, fuels can become unstable with respect to peroxide formation when their sulfur content is reduced to low levels by hydroprocessing. Vardi et al also describe how compounds like tetralin can cause fuels to become unstable with respect to peroxide formation, while polycyclic aromatic compounds like naphthalenes can improve stability. Vardi et al. explains that aromatics act as natural antioxidants and notes that natural peroxide inhibitors such as sulfur compounds and polycyclic aromatics can be removed. [0008] Following on the work by Vardi, two recent patents from Exxon describe how the peroxide-stability of highly-paraffinic Fischer Tropsch products in unacceptable, but can be improved by the addition of sulfur compounds from other blend components. However, since sulfur compounds increase sulfur emissions, this approach is not desirable. [0009] By way of example, U.S. Pat. No. 6,162,956 discloses a Fischer-Tropsch derived distillate fraction blended with either a raw gas field condensate distillate fraction or a mildly hydrotreated condensate fraction to obtain a stable, inhibited distillate fuel. The fuel is described as a blend material useful as a distillate fuel or as a blending component for a distillate fuel comprising: (a) a Fischer-Tropsch derived distillate comprising a C.sub.8-700.degree. F. fraction, and (b) a gas field condensate distillate comprising a C.sub.8-700.degree. F. fraction, wherein the sulfur content of the blend material is .gtoreq.1 ppm by wt. This patent discloses that distillate fuels derived from Fischer-Tropsch processes are hydrotreated to eliminate unsaturated materials, e.g., olefins, and most, if not all, oxygenates. This patent further discloses that the products contain less than or equal to 0.5 wt % unsaturates (olefins and aromatics). [0010] Similarly, U.S. Pat. No. 6,180,842 discloses a Fischer-Tropsch derived distillate fraction blended with either a raw virgin condensate fraction or a mildly hydrotreated virgin condensate to obtain a stable inhibited distillate fuel. The fuel is describes as a blend material useful as a distillate fuel or as a blending component for a distillate fuel comprising (a) a Fischer-Tropsch derived distillate comprising a C.sub.8-700.degree. F. stream and having a sulfur content of less than 1 ppm by wt, and (b) 1-40 wt % of a virgin distillate comprising a C.sub.8-700.degree. F. stream; wherein the sulfur content of the blend material is .gtoreq.2 ppm by wt. This patent notes that while there is no standard for the peroxide content of fuels, there is general acceptance that stable fuels have a peroxide number of less than about 5 ppm, preferably less than about 4 ppm, and desirably less than about 1 ppm. This value is tested after storage at 60.degree. C. in an oven for 4 weeks. The patent shows that Fischer Tropsch products having a peroxide number of 24.06 after 4 weeks have unacceptable stability. [0011] The Fischer Tropsch products in the '842 patent are described as being >80 wt %, preferably >90 wt %, more preferably >95 wt % paraffins, having an iso/normal ratio of 0.1 to 10, preferably 0.3 to 3.0, more preferably 0.7 to 2.0; sulfur and nitrogen of less than 1 ppm each, preferably less than 0.5, more preferably less than 0.1 ppm each; .ltoreq.0.5 wt % unsaturates (olefins and aromatics), preferably .ltoreq.0.1 wt %; and less than 0.5 wt % oxygen on a water free basis, preferably less than about 0.3 wt % oxygen, more preferably less than 0.1 wt % oxygen and most preferably nil oxygen. The '842 patent teaches that the Fischer Tropsch distillate is essentially free of acids. [0012] U.S. Pat. No. 5,689,031 demonstrates that olefins in low-sulfur diesel fuel contribute to peroxide formation. See Fuels C and D in Example 7, and FIG. 2. The '031 patent teaches that the solution to the peroxide forming tendency is to limit the olefin content by hydrotreating the lightest olefin fraction. However, this solution requires the use of expensive hydrogen gas. [0013] Accordingly, there is a need in the art for low sulfur distillate fuels and distillate fuel blend stocks with satisfactory stability, which can be obtained from Fischer-Tropsch process products while minimizing the use of expensive hydrogen. This invention provides such distillate fuels and distillate fuel blend stocks and the processes for their manufacture. SUMMARY OF THE INVENTION [0014] The present invention relates to a distillate fuel comprising a Fischer-Tropsch distillate fuel blend stock. The Fischer Tropsch distillate fuel blend stock comprises unsaturates in an amount between 2 and 20 weight %, paraffins in an amount 80 weight % or greater, sulfur in an amount less than 1 ppm, and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks, and the Fischer Tropsch distillate fuel blend stock has a cetane index of greater than 60. [0015] In another embodiment, the present invention relates to a Fischer-Tropsch diesel fuel blend stock. The Fischer Tropsch diesel fuel blend stock comprises unsaturates in an amount between 2 and 20 weight %, paraffins in an amount 90 weight % or greater, sulfur in an amount less than 1 ppm and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks. The unsaturates comprise less than 20 weight % polynuclear aromatics, preferably less than 10 weight % polynuclear aromatics, and even more preferably less than 5 weight % polynuclear aromatics. Preferably the unsaturates comprise both olefins and aromatics, and most preferably the olefins are present in amounts greater than or equal to 1 wt %. Characteristics of the diesel fuel blend stock include a cetane index greater than 60, a percent reflectance according to ASTM D6468 at 150.degree. C. in excess of 65% when measured at 90 minutes. [0016] In yet another embodiment, the present invention relates to a Fischer-Tropsch jet fuel blend stock. The Fischer Tropsch jet fuel blend stock comprises unsaturates in an amount between 2 and 10 weight %, paraffins in an amount 90 weight % or greater, sulfur in an amount less than 1 ppm, and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks. The unsaturates comprise less than 20 weight % polynuclear aromatics, preferably less than 5 weight % polynuclear aromatics, and even more preferably less than 5 weight % polynuclear aromatics. Characteristics of the jet fuel blend stock include a smoke point of 30 mm or greater, and a passing rating in ASTM D3241 (JFTOT Procedure) at 260.degree. C. for 2.5 hours. [0017] In a further embodiment, the present invention relates to a process for preparing a highly paraffinic, moderately unsaturated distillate fuel blend stock. The process comprises converting syngas to a Fischer Tropsch derived feedstock by a Fischer Tropsch process and hydroprocessing the Fischer-Tropsch derived feedstock. A highly paraffinic, moderately unsaturated distillate fuel blend stock is recovered. The highly paraffinic, moderately unsaturated distillate fuel blend stock contains between 2 and 20 weight % unsaturates less than 1 ppm sulfur, and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks. The hydroprocessing conditions include a temperature of 600-750.degree. F., a pressure of less than 1000 psig, and a liquid hourly space velocity of greater than 0.25 hr.sup.-1. [0018] In yet a further embodiment the present invention relates to a distillate fuel comprising a Fischer Tropsch distillate fuel blend stock, wherein the Fischer Tropsch distillate fuel blend stock is made by a process comprising converting syngas to a Fischer Tropsch derived feedstock by a Fischer Tropsch process; hydroprocessing the Fischer-Tropsch derived feedstock at a temperature of 525-775.degree. F., a pressure of less than 1000 psig, and a liquid hourly space velocity of greater than 0.25 hr.sup.-1; and recovering a Fischer Tropsch distillate fuel blend stock. The Fischer Tropsch distillate fuel blend stock, which is recovered, comprises between 2 and 20 weight % unsaturates, less than 1 ppm sulfur, and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks. [0019] In a further embodiment, the present invention relates to a method of operating a diesel engine comprising using a Fischer Tropsch diesel fuel blend stock as a diesel fuel wherein the Fischer Tropsch diesel fuel blend stock comprises unsaturates in an amount between 2 and 20 weight %, paraffins in an amount 90 weight % or greater, sulfur in an amount less than 1 ppm and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks. The unsaturates comprise less than 20 weight % polynuclear aromatics, preferably less than 10 weight % polynuclear aromatics, and even more preferably less than 5 weight % polynuclear aromatics. Preferably the unsaturates comprise both olefins and aromatics, and most preferably the olefins are present in amounts greater than or equal to 1 wt %. Characteristics of the diesel fuel blend stock include a cetane index greater than 60, a percent reflectance according to ASTM D6468 at 150.degree. C. in excess of 65% when measured at 90 minutes. [0020] In yet another embodiment, the present invention relates to a method of operating a jet engine comprising using a Fischer Tropsch jet fuel blend stock as a jet fuel wherein the Fischer Tropsch jet fuel blend stock comprises unsaturates in an amount between 2 and 10 weight %, paraffins in an amount 90 weight % or greater, sulfur in an amount less than 1 ppm, and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60.degree. C. for four weeks. The unsaturates comprise less than 20 weight % polynuclear aromatics, preferably less than 5 weight % polynuclear aromatics, and even more preferably less than 5 weight % polynuclear aromatics. Characteristics of the jet fuel blend stock include a smoke point of 30 mm or greater, and a passing rating in ASTM D3241 (JFTOT Procedure) at 260.degree. C. for 2.5 hours. Continue reading about Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products... Full patent description for Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products or other areas of interest. ### Previous Patent Application: Highly paraffinic, moderately aromatic distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products Next Patent Application: Process for the catalytic hydrotretment of heavy hydrocarbons of petroleum Industry Class: Mineral oils: processes and products ### FreshPatents.com Support Thank you for viewing the Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products patent info. IP-related news and info Results in 0.36059 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
