Patent Publication Number: US-2011061290-A1

Title: Aviation-grade kerosene from independently produced blendstocks

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application which claims the benefit under 35 U.S.C. §121 of U.S. patent application Ser. No. 12/147,783, filed Jun. 27, 2008, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/947,126, filed Jun. 29, 2007, the disclosures of each of which are hereby incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under contract W911NF-07-C-0046 awarded by the Defense Advanced Research Projects Agency (DARPA). The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to aviation-grade high-cetane kerosene fuel. More particularly, herein disclosed is an aviation-grade kerosene fuel produced in part or fully from non-petroleum feedstocks. Specifically, the disclosed kerosene fuel comprises at least two independently produced blendstocks, with the first blendstock comprising primarily isoparaffins and normal paraffins (I/N) derived from non-petroleum feedstocks and the second blendstock comprising primarily cycloalkanes and aromatics (C/A) derived from petroleum or non-petroleum feedstocks. In embodiments, a kerosene fuel suitable for use as aviation turbine fuel having drop-in and fit-for-purpose compatibility with conventional petroleum-derived fuels comprises up to 95 volume percent (vol. %) I/N blendstock and up to 35 vol. % C/A blendstock. 
     2. Background of the Invention 
     The generic term “kerosene” is used to describe the fraction of crude petroleum that boils approximately in the range of 293° F. to 572° F. (145° C. to 300° C.) and consists of hydrocarbons primarily in the range of C 8 -C 16 . Kerosenes are the lighter end of a group of petroleum substances known as middle distillates. 
     As an example, the predominant use of high-cetane kerosene in the United States is aviation turbine fuel for civilian (Jet A or Jet A-1) and military (JP-8 or JP-5) aircraft. Kerosene-based fuels differ from each other in performance specifications. Jet A and Jet A-1 are kerosene-type fuels. The primary physical difference between Jet A and Jet A-1 is freeze point (the temperature at which wax crystals disappear in a laboratory test). Jet A, which is mainly used in the United States, must have a freeze point of −40° C. or below, while Jet A-1 must have a freeze point of −47° C. or below. Jet A does not normally contain a static dissipater additive, while Jet A-1 often requires this additive. There are additional differences between the two fuels, and full specifications are outlined under the ASTM D1655 and Def Stan 91-91/5 standards, respectively. 
     Military turbine fuel grades such as JP-5 and JP-8 are defined by Mil-DTL-5624 and Mil-DTL-83133, respectively. These fuels are kerosene-type fuels made to more exacting specifications than the commercial jet fuels. They also contain unique performance enhancing additives. Throughout the world, many governments have issued a variety of standards such as for TS-1 premium kerosene, TS-1 regular kerosene, and T-1 regular kerosene in Russia. The crude oil fraction for all of these aviation-grade kerosenes is basically limited to the range of 300° F. to 500° F. (149° C. to 260° C.), with additional specifications based on recovery rates at given temperature points. Hydrocarbons are primarily in the range of C 8 -C 16 . 
     The ready availability of crude petroleum has encouraged the establishment of the above-mentioned specifications for kerosene as the basis for fuels in engines of various types, and engines have thus been optimized to run on kerosene having these specifications. Concern has arisen regarding the reliability and availability of the petroleum supply. This concern has stimulated a search for substitutes. Liquids derived from coal, shale, tar sands, and renewable resources such as biomass, in particular, plant material, have been proposed. These processes have not adequately produced aviation-grade kerosene that complies with today&#39;s jet fuel specifications. 
     The failure of obtaining suitable aviation-grade kerosenes from non-petroleum feedstocks has triggered development in downstream processing of the products. For example, U.S. Pat. No. 4,645,585 discloses the production of novel fuel blends from hydroprocessing highly aromatic heavy oils such as those derived from coal pyrolysis and coal hydrogenation. 
     International Patent WO 2005/001002 A2 relates to a distillate fuel comprising a stable, low-sulfur, highly paraffinic, moderately unsaturated distillate fuel blendstock. The highly paraffinic, moderately unsaturated distillate fuel blendstock is prepared from a Fischer-Tropsch-derived product that is hydroprocessed under conditions during which a moderate amount of unsaturates are formed or retained to improve stability of the product. 
     Although many physical properties for aviation-grade kerosene can be matched and even outperformed, the fuels derived by hydroprocessing and additional upgrading as described above do not provide drop-in compatibility with conventional petroleum-derived aviation-grade kerosene, as they lack some of the major hydrocarbon constituents of typical petroleum-derived kerosene. 
     An attempt for better modeling of the variety of different hydrocarbon constituents was made by Violi et al. (Violi, A.; Yan, S.; Eddings, E. G.; Sarofim, A. F.; Granata, S.; Faravelli, T.; Ranzi, E.;  Combust. Sci. Technol.  2002, 174 (11-12) 399-417). Violi et al. modeled JP-8 as a six-compound blend of well-known hydrocarbons with the following molar composition: 10% iso-octane (C 8 H 18 ), 20% methylcyclohexane (C 7 H 14 ), 15% m-xylene (C 8 H 10 ), 30% normal-dodecane (C 12 H 26 ), 5% tetralin (C 10 H 12 ), and 20% tetradecane (C 14 H 30 ). This surrogate blend simulates the volatility and smoke point of a practical JP-8 fuel. However, this method of reducing the fuel to a mere six-compound blend does not reproduce all required performance specifications of JP-8. 
     A different route was pursued in U.S. Patent Application 2006/0138025, which relates to distillate fuels or distillate fuel blendstocks comprising a blend of a Fischer-Tropsch-derived product and a petroleum-derived product that is then hydrocracked under conditions to preserve aromatics. While this may produce some required characteristics from certain petroleum feedstocks, such as seal swell and density, this approach reduces the ability to achieve competing characteristics, such as freeze point specifications. 
     Accordingly, there is an ongoing need for a fuel and process that allow use of environmentally-sensitive processes as a bridge to the future and provide drop-in compatibility with existing petroleum-based aviation-grade kerosene for clean fuels produced from secure domestic resources. 
     SUMMARY 
     Herein disclosed is aviation-grade kerosene comprising: a first blendstock derived from non-petroleum feedstock and comprising primarily hydrocarbons selected from the group consisting of isoparaffins and normal paraffins, and a second blendstock comprising primarily hydrocarbons selected from the group consisting of cycloalkanes and aromatics. In embodiments, the second blendstock is derived from feedstock comprising non-petroleum feedstock. It is desirable for the aviation-grade kerosene is capable of being blended with petroleum-derived jet fuel in any proportion such that the resulting blend meets fuel grade specification of the petroleum-derived jet fuel. In embodiments, the aviation-grade kerosene comprises up to 95 vol. % of first blendstock and up to 35 vol. % of second blendstock. 
     In specific embodiments, the aviation-grade kerosene comprises up to 95 vol. % first blendstock, from about 0 vol. % to about 30 vol. % cycloalkanes, and from about 0 vol. % to about 15 vol. % aromatics. In embodiments, this kerosene comprising up to 95 vol. % first blendstock, from about 0 vol. % to about 30 vol. % cycloalkanes, and from about 0 vol. % to about 15 vol. % aromatics meets fit-for-purpose requirements. In embodiments, at least 50 weight percent of the kerosene is derived from coal, natural gas, or a combination thereof. In embodiments, the second blendstock is derived from coal, biomass, oil-shale, tar, oil sands, or a combination thereof. In embodiments, at least 50 weight percent of the kerosene is derived from biomass. In embodiments, at least 10 weight percent of the kerosene is derived from non-cracked bio-oil. 
     Also disclosed herein is a method for the production of aviation-grade kerosene comprising: producing a first blendstock from at least one non-petroleum feedstock, the first blendstock comprising primarily hydrocarbons selected from the group consisting of isoparaffins and normal paraffins; producing a second blendstock comprising primarily hydrocarbons selected from the group consisting of cycloalkanes and aromatics; and blending at least a portion of the first blendstock with at least a portion of the second blendstock to produce aviation-grade kerosene. In embodiments of the method for the production of aviation-grade kerosene, first and second blendstocks are independently-produced. In embodiments of the method, the non-petroleum feedstock is selected from the group consisting of coal, natural gas, biomass, vegetable oils, biomass pyrolysis bio-oils, biologically-derived oils and combinations thereof. 
     In some embodiments of the method, at least a portion of first blendstock is produced via indirect liquefaction. Indirect liquefaction may comprise Fischer-Tropsch processing of a feedstock selected from the group consisting of natural gas, coal, biomass, and combinations thereof. The kerosene may comprise up to about 90 vol. % first blendstock produced via indirect liquefaction. 
     In embodiments of the method for the production of aviation-grade kerosene, the at least one non-petroleum feedstock comprises triglyceride and/or fatty acid feedstock. The kerosene may comprise from about 65 vol. % to about 75 vol. % of first blendstock, the at least one non-petroleum feedstock for which comprises triglyceride and/or fatty acid feedstock. In embodiments, second blendstock is produced by catalytic cyclization and/or reforming of a portion of first blendstock, the at least one non-petroleum feedstock for which comprises triglyceride and/or fatty acid feedstock. The kerosene may comprise about 65 vol. % first blendstock, the at least one non-petroleum feedstock for which comprises triglyceride and/or fatty acid feedstock; and about 35 vol. % second blendstock produced by catalytic cyclization and/or reforming of a portion of first blendstock. 
     In some embodiments, the kerosene comprises about 70 vol. % first blendstock produced via catalytic processing of triglyceride and/or fatty acid feedstock and about 30 vol. % second blendstock produced via pyrolysis processing of high cycloalkane-content material. 
     In embodiments of the method for the production of aviation-grade kerosene, second blendstock is produced via pyrolysis of a feedstock selected from the group consisting of coal, oil shale, oil sands, tar, biomass, and combinations thereof. In specific embodiments, the kerosene may comprise about 80 vol. % first blendstock produced via Fischer-Tropsch processing of natural gas, coal, and/or biomass and about 20 vol. % second blendstock produced via pyrolysis processing of coal tar fraction. 
     In some embodiments of the method for the production of aviation-grade kerosene, the second blendstock is produced via direct liquefaction. In embodiments, the kerosene comprises about 25 vol. % second blendstock produced via direct liquefaction. In specific embodiments, the kerosene further comprises about 75 vol. % first blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass. 
     In some embodiments of the method for the production of aviation-grade kerosene, second blendstock is produced from a biomass-derived lignin feedstock. The kerosene may comprise from about 25 vol. % to about 30 vol. % second blendstock produced from a biomass-derived lignin feedstock. In some embodiments, the kerosene comprises about 30 vol. % second blendstock produced via pyrolysis processing of biomass-derived lignin and about 70 vol. % first blendstock produced via Fischer-Tropsch processing of natural gas, coal, and/or biomass. In embodiments, the kerosene comprises about 25 vol. % second blendstock produced from a biomass-derived lignin feedstock and about 75 vol. % first blendstock derived from catalytic processing of triglyceride feedstock. 
     In embodiments of the method for the production of aviation-grade kerosene, the method further comprises testing the aviation grade kerosene for at least one requirement selected from the group consisting of fit-for-purpose requirements, ASTM requirements, and combinations thereof. In embodiments, the method further comprises adjusting the ratio of first blendstock and second blendstock in the kerosene to meet at least one requirement selected from the group consisting of fit-for-purpose requirements, ASTM requirements, and combinations thereof. In some embodiments, the method further comprises adjusting the amount of cycloalkanes and aromatics in the second blendstock to meet at least one requirement selected from the group consisting of fit-for-purpose requirements, ASTM requirements, and combinations thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic of an indirect liquefaction process suitable for producing isoparaffin/n-paraffin (I/N) blendstock according to an embodiment of the present disclosure. 
         FIG. 2  is a schematic of a pyrolysis process suitable for producing cycloalkane/aromatic (C/A) blendstock according to an embodiment of the present disclosure. 
         FIG. 3  is a schematic of a direct liquefaction process suitable for producing cycloalkane/aromatic (C/A) blendstock according to an embodiment of the present disclosure. 
         FIG. 4  is a comparison of gas chromatography data from FT (FT derived liquid fuel from natural gas—bottom) and Fuel Sample A (top) produced from two discrete blendstocks and technological processes: (1) an isoparaffinic kerosene (IPK) produced from FT technology and natural gas feedstock and (2) an aromatic/cycloparaffinic blendstock produced from petroleum feedstock. 
         FIG. 5  is a comparison of gas chromatography data from typical JP-8 (bottom) and Fuel Sample C (top) produced from two discrete blendstocks and technological processes: (1) an isoparaffinic kerosene (IPK) produced from a crop oil feedstock and (2) an aromatic/cycloparaffinic blendstock produced from a crop oil feedstock. 
     
    
    
     NOTATION AND NOMENCLATURE 
     The term “I/N blendstock” as used herein refers to a material that comprises at least 95 weight percent of isoparaffins, normal paraffins, or a mixture thereof. 
     The term “C/A blendstock” as used herein refers to a material that comprises at least 95 weight percent of cycloalkanes, aromatics, or a mixture thereof. 
     The terms “aviation-grade kerosene” or “jet fuel” as used herein refer to kerosene-type fuels that are specified by military turbine fuel grades such as JP-5 and JP-8 and defined by Mil-DTL-5624 and Mil-DTL-83133, respectively, or civilian aviation jet fuels such as Jet A or Jet A-1 with full specifications outlined under the ASTM D1655 and Def Stan 91-91/5 standards, respectively. Throughout the world there exist a variety of similar standards that might change over time and are considered under this definition. 
     The term “fit-for-purpose requirements” as used herein refers to fuel property requirements that are not necessarily addressed by military or ASTM standards, but are still important to fuel performance and stability in jet engines and during fuel handling, distribution, and storage. Examples of fit-for-purpose requirements include fuel compatibility with aircraft fuel and engine system materials of construction, adequate fuel performance in compression ignition (versus turbine) engines in a wide variety of ground environments, and possible fuel performance requirements related to swelling of elastomeric seals in, for example, turbine engines. 
     The term “drop-in compatibility” as used herein refers to aviation-grade kerosene capable of being blended with petroleum-derived jet fuel in any proportion (i.e. from 0% to 100%) such that the resulting blend meets fuel grade specification and fit-for-purpose requirements of the equivalent petroleum-based jet fuel. 
     The term “I/N-C/A fuel” as used herein refers to aviation-grade kerosene derived from at least two independently produced blendstocks, with a first I/N blendstock derived from non-petroleum feedstocks and a second C/A blendstock derived from petroleum or non-petroleum feedstocks. 
     DETAILED DESCRIPTION 
     I. Overview 
     Herein disclosed are a fuel and a method for making the fuel whereby the fuel has drop-in compatibility with existing petroleum-derived fuels and enables production of most or all of a fuel from domestic, non-petroleum, and/or renewable feedstocks. The method of making this aviation-grade jet fuel may allow broad flexibility in fuel formulation in order to meet specific end-use requirements. The disclosed I/N-C/A fuel comprises a blend of fuel components, namely straight-chain (normal) and branched (iso-) paraffins, cycloalkanes, and/or aromatics. 
     Meeting a specification for aviation-grade kerosene requires providing a complex mixture of fuel chemical classes that have conflicting effects on physical properties. For example, longer carbon chain molecules serve to reduce volatility and increase density, which in turn raises freeze point above acceptable levels for high altitude flight. Balancing these characteristics along with energy density, flash point, viscosity, smoke point, seal-swelling capacity, and other characteristics makes fuel formulation difficult when derived from a single non-petroleum resource. 
     The aviation-grade kerosene herein disclosed is produced from at least two independently-produced blendstocks, with a first blendstock comprising primarily hydrocarbons selected from the group consisting of isoparaffins and normal paraffins (I/N) and derived from non-petroleum feedstocks and a second blendstock comprising primarily hydrocarbons selected from the group consisting of cycloalkanes and aromatics (C/A) and derived from petroleum or non-petroleum feedstocks. In embodiments, the finished I/N-C/A jet fuel comprises up to 95 volume percent (vol. %) I/N blendstock and up to 35 (vol. %) C/A blendstock. 
     II. Kerosene 
     Petroleum-based kerosene may be obtained either from the atmospheric distillation of crude oil (“straight-run” kerosene) or from cracking of heavier petroleum streams (“cracked” kerosene). The kerosene is further treated by a variety of processes to remove or reduce the level of undesirable components, e.g., aromatic hydrocarbons, sulfur, nitrogen, or olefinic materials. This additional processing also reduces compositional variation and enriches components that improve performance (cycloalkanes and isoparaffins, for example). In practice, the major processes used are hydrodesulfurization (treatment with hydrogen to remove sulfur components), washing with caustic soda solution (to remove sulfur components), and hydrogenation (to remove, for example, olefins, sulfur, metals, and/or nitrogen components). Aromatics that may have formed during the cracking process are removed via solvent extraction. For instance, hydrodesulfurized kerosene is obtained by treating a kerosene-range petroleum stock with hydrogen to convert organic sulfur to hydrogen sulfide, which is then removed. These subsequent treatments may blur the distinction between straight-run and cracked kerosenes. 
     While kerosenes are essentially similar in composition, the precise composition of a specific kerosene-range refinery stream depends on the crude oil from which the kerosene was derived and on the refinery processes used for its production. Because they are complex hydrocarbon mixtures, materials in this category are typically not defined by detailed compositional data but instead by process history, physical properties, and product-use ASTM and similar specifications. 
     Consequently, detailed compositional information for the streams in this category is limited. General compositional information on representative kerosene-range refinery streams and fuels, presented in Table 1, illustrates the fact that the materials in this category are similar in physical properties and composition. Regardless of crude oil source or processing history, major components of kerosenes comprise branched and straight-chain paraffins (iso- and normal or n-alkanes) and naphthenes (cycloparaffins or cycloalkanes), which normally account for at least 75 vol. % of a finished fuel. Aromatic hydrocarbons in this boiling range, such as alkylbenzenes (single ring) and alkylnaphthalenes (double ring) do not normally exceed 25 vol. % of a kerosene product. Olefins are usually not present at more than 5% by volume. The distillation range of kerosenes is such that benzene (80° C. boiling point) and normal-hexane (69° C. boiling point) concentrations are generally less than 0.01% by mass. The boiling points of the 3-7 fused-ring polycyclic aromatic compounds (PACs) are well above the boiling range of straight-run kerosene streams. Consequently, the concentrations of PACs found in kerosenes are very low, if not below the limits of detection of the available analytical methods. A detailed analysis of a hydrodesulfurized kerosene illustrates this and is presented as Table 2. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 General Kerosene Compositional Information 
               
            
           
           
               
               
               
               
            
               
                   
                 Hydrodesulfurized 
                   
                   
               
               
                   
                 Kerosene 
                 Jet A 
                 JP-8 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 API Gravity 
                   39-45.5 
                 37.2-46.1 
                 37.0-46.7 
               
               
                 Aromatic Content, vol. % 
                   18-21.4 
                 11.6-24.0 
                 13.6-22.1 
               
               
                 Olefin Content, vol. % 
                  1.0-1.66 
                 0.0-4.1 
                 0.6-3.0 
               
               
                 Saturates Content, vol. % 
                 77.2-82   
                 71.9-88.4 
                 74.9-85.8 
               
               
                 10% Distillation, ° F. 
                 329-406 
                 294-394 
                 333-390 
               
               
                 FBP Distillation, ° F. 
                 451-568 
                 404-510 
                 419-474 
               
               
                 (Final Boiling Pt.) 
                   
                 (90%) 
                 (90%) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Hydrodesulfurized Kerosene 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Weight Percent 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Nonaromatics 
                 80.27 
               
               
                   
                 Saturates 
                 78.61 
               
               
                   
                 Olefins 
                 1.66 
               
               
                   
                 Aromatics 
                 19.72 
               
               
                   
                 Less than Three-Ring PAC 
                 19.72 
               
               
                   
                 Three- to Seven-Ring PAC 
                 &lt;0.01 
               
               
                   
                   
               
            
           
         
       
     
     III. I/N Blendstock 
     The herein disclosed I/N-C/A blend fuel comprises at least one I/N blendstock comprising primarily hydrocarbons selected from the group consisting of isoparaffins and normal paraffins, the hydrocarbons derived from non-petroleum feedstock. The finished I/N-C/A jet fuel comprises up to 95 vol. % of I/N blendstock. In embodiments, I/N blendstock comprises isoparaffin and/or normal paraffin compounds containing primarily from eight to sixteen carbon atoms per molecule (C8 to C16 compounds). In embodiments, these compounds are produced directly via a chemical process such as, but not limited to, Fischer-Tropsch condensation of synthesis gas (‘syngas’), thermocatalytic processing of vegetable oils, pyrolysis, liquefaction, and gas-to-liquids processing. 
     In embodiments, I/N blendstock is derived from one or a combination of the following feedstocks: natural gas, coal, biomass, vegetable oils, biomass pyrolysis bio-oils, and other biologically-derived oils. I/N blendstock can be produced by several routes. In a specific embodiment, as shown in  FIG. 1 , indirect liquefaction is used to produce I/N blendstock. Indirect liquefaction feedstock, such as coal or biomass,  10  is gasified in gasifier  40  with steam  20  and/or oil  30 . Gasifier effluent  50 , may comprise carbon monoxide, hydrogen, carbon dioxide, hydrogen sulfide, and/or ammonia. Gasifier effluent  50  is purified and upgraded in step  60 , whereby a contaminant stream(s)  70  comprising, for example, hydrogen sulfide, ammonia, and/or carbon dioxide is removed. Syngas stream  80 , comprising primarily CO and H 2 , undergoes liquefaction  90  to yield liquid products  100 . In embodiments, liquid products  100  are synthesized from syngas  80  by catalytic Fischer-Tropsch (F-T) processing. The Fischer-Tropsch reactions produce a wide spectrum of oxygenated compounds, in particular, alcohols and paraffins ranging in carbon numbers from C 1 -C 3  (gases) to C 35+  (solid waxes). These Fischer-Tropsch products yield distillate fuels that comprise C 8 -C 16  paraffins and, through isomerization, C 8 -C 16  isoparaffins that have excellent cetane numbers and very low sulfur and aromatic content. These properties make F-T products suitable for use as I/N blendstock. However, because of the lack of adequate cycloalkanes and aromatics, Fischer-Tropsch distillate fuels are typically unable to meet all military and ASTM specifications and fit-for-purpose requirements. Therefore, as described further hereinbelow, I/N blendstock is blended with C/A blendstock to obtain aviation-grade I/N-C/A fuel. In embodiments, I/N-C/A fuel comprises up to 95 vol. % I/N blendstock, alternatively about 90 vol. % I/N blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass. In embodiments, the I/N-C/A fuel comprises about 80 vol. % I/N blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass. In alternative embodiments, I/N-C/A fuel comprises about 70 vol. % I/N blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass. 
     In embodiments, I/N blendstock is produced from triglyceride and/or fatty acid feedstocks. I/N blendstock n-paraffins may be produced, for example, via: (1) catalytic triglyceride dissociation into fatty acids and glycerol, (2) glycerol removal, and (3) oxygen removal from fatty acids (e.g., via catalytic decarboxylation and/or reduction) to yield normal paraffins. I/N blendstock isoparaffins may be produced via (4) catalytic isomerization of a portion of these normal paraffins to yield isoparaffins. 
     In embodiments, I/N-C/A fuel comprises from about 65 vol. % to about 95 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock. In specific embodiments, I/N-C/A fuel comprises about 75 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock. In alternative embodiments, I/N-C/A fuel comprises about 80 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock. In alternative embodiments, I/N-C/A fuel comprises about 80 to 90 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock. 
     IV. C/A Blendstock 
     As mentioned hereinabove, I/N blendstock typically has a density below minimum requirements. For example, the I/N blendstock typically has a density below the MIL-DTL-83133-specified minimum requirement of 0.775 kg/L and may be very near to exceeding or may exceed the freeze point maximum requirement of less than −47° C. As it is desirable for the I/N-C/A fuel to meet standard (for example, MIL-DTL-83133-specified) density, freeze point, and flash point requirements, the disclosed I/N-C/A fuel further comprises at least one independently-produced C/A blendstock to obtain required density and cold-flow performance. The C/A blendstock comprises primarily hydrocarbons selected from the group consisting of cycloalkanes and aromatics. The aviation-grade I/N-C/A fuel comprises an appropriate blend of aromatics and cycloalkanes whereby requisite density and freeze point specifications of the resulting high cetane kerosene fuel are met. In embodiments, the hydrocarbons of the C/A blendstock are derived from petroleum feedstocks. In embodiments, the hydrocarbons of the C/A blendstock are derived from non-petroleum feedstocks. In embodiments, the hydrocarbons of the C/A blendstock are derived from a combination of petroleum and non-petroleum feedstocks. In embodiments, the I/N-C/A fuel comprises up to 35 vol. % C/A blendstock. 
     In embodiments, the C/A blendstock comprises aromatics. In embodiments, the C/A blendstock comprises aromatics selected primarily from the group consisting of C9 to C15 aromatics which provide the requisite density. In embodiments, the aromatics are primarily alkylated benzene compounds. In addition to providing density, aromatics may also contribute to beneficial seal swelling and may provide needed lubricity and viscosity. In embodiments, the C/A blendstock comprises less than about 15 vol. % aromatics. In embodiments, the C/A blendstock comprises from about 0 vol. % to about 15 vol. % aromatics. 
     In embodiments, C/A blendstock comprises cycloalkanes. In embodiments, the C/A blendstock comprises cycloalkanes primarily selected from the group consisting of C 9  to C 15  cycloalkanes which reduce freeze point (to counteract the freeze point increase resulting from aromatic addition) without adversely decreasing flash point. In embodiments, C/A blendstock comprises less than about 30 vol. % cycloalkane. In embodiments, suitable freezepoint are obtained in the I/N-C/A fuel by selection of aromatics (i.e. having high density and low freezepoint) for the C/A blendstock such that the C/A blendstock comprises 0% cycloalkanes. In embodiments, C/A blendstock comprises from about 0 vol. % to about 30 vol. % cycloalkane. In embodiments, jet-fuel compliant I/N-C/A fuel comprises up to 95 vol. % of paraffins selected from isoparaffins and normal paraffins, from about 0 vol. % to about 30 vol. % cycloalkanes, and from about 0 vol. % to about 15 vol. % aromatics. In embodiments, I/N-C/A fuel comprises about 95 vol. % I/N blendstock and about 5% high density low freezepoint aromatic. 
     Without limitation, C/A blendstock may be derived from one or a combination of the following feedstocks: petroleum, oil shale, oil sands, natural gas, coal, biomass, vegetable oil, biomass pyrolysis bio-oil, and other biologically-derived oils. In embodiments, aviation-grade I/N-C/A kerosene comprises at least 50 weight percent of hydrocarbons selected from cycloalkanes and aromatics, said hydrocarbons derived from coal, biomass, or a combination thereof. 
     C/A blendstock may be produced by several methods.  FIG. 2  shows an embodiment for the production of C/A blendstock via pyrolysis (heating in a deficiency of oxygen). Pyrolysis may be performed by any method known to one of skill in the art. In  FIG. 2 , pyrolysis feedstock  110  undergoes pyrolysis  120 . Suitable pyrolysis feedstock  110  includes, without limitation, coal, oil shale, oil sands, biomass, and combinations thereof. Gases  140  and char/ash/minerals  130  are removed. Pyrolysis oil vapors are condensed, the resulting pyrolysis oil  150  is hydrotreated as is known to those of skill in the art. In embodiments, catalytic hydrotreating is used to reduce the level of at least one contaminant selected from the group consisting of nitrogen, sulfur, oxygen, and metals. In embodiments, pyrolysis oil  150  is treated with hydrogen  180  and the level of sulfur and/or nitrogen in pyrolysis oil  150  is reduced via elimination of gas stream(s)  170  comprising, for example, hydrogen sulfide and/or ammonia. Via hydrotreating  160 , contaminant-reduced liquid products  190  are obtained. This procedure is similar to the procedure used in upgrading crude oil in a refinery to produce a variety of liquid fuels, as known to those of skill in the art. Table 3 presents a comparison of pyrolyzed coal tar fractions based on typical boiling range and major hydrocarbon constituents. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Typical Coal Tar Fractions 
               
            
           
           
               
               
               
            
               
                   
                 Boiling 
                 Typical HC Constituents 
               
               
                 Fraction 
                 Range, ° C. 
                 and Carbon Numbers 
               
               
                   
               
               
                 Ammoniacal Liquor 
                 ~100 
                 — 
               
               
                 Light Oil 
                 &lt;170 
                 Benzene, C 6 ; Toluene, C 7 ; 
               
               
                   
                   
                 Xylene, C 8   
               
               
                 Middle Oil or Carbolic Oil 
                 170-230 
                 Naphthalene, C 10   
               
               
                 Heavy Oil or Creosote Oil 
                 230-270 
                 Naphthalene, C 10   
               
               
                 Green Oil or Anthracene Oil 
                 270-360 
                 Anthracene, C 14   
               
               
                 Residue or Pitch 
                 &gt;360 
                 — 
               
               
                   
               
            
           
         
       
     
     In particular, low-temperature tar and light oils formed from sub-bituminous and bituminous coals at temperatures below about 700° C. as relatively fluid, dark brown oils that comprise phenols, pyridines, paraffins, and/or olefins. The oils are heterogeneous, with any one component constituting only a fraction of a percent of the total mass. The lignite tars may also contain up to 10% of paraffin waxes, so the product has a “butter-like consistency” and solidifies at temperatures as high as 6° C. to 8° C. The primary high-temperature tar vapors formed above 700° C. are more homogeneous. The light oils are predominantly benzene, toluene, and xylenes (BTX) and the tars are bitumen-like viscous mixtures that contain high proportions of polycondensed aromatics. For the most part, the pyrolysis tars and oils are not suitable final fuel products. Often they are unstable, and when warmed, they polymerize and become more viscous. Ash and mineral matter  130  is removed in pyrolysis  120 , which increases the heating value, but sulfur and nitrogen are not completely removed in pyrolysis  120 . A more stable and useful product is obtained by hydrogenating  160  and removing the sulfur and/or nitrogen from the fuel as hydrogen sulfide and/or ammonia in stream(s)  170 . These procedures are, as noted previously, similar to the various refinery procedures used to upgrade natural crude oils. The hydrotreated liquid products  190  may be further refined and upgraded, by any methods known to one of skill in the art, to yield a mix of cycloalkanes and aromatics of which the C/A blendstock is comprised. 
     In embodiments, the I/N-C/A fuel comprises about 20 vol. % C/A blendstock derived from pyrolysis processing of a coal tar fraction. In embodiments, the I/N-C/A fuel comprises about 80 vol. % I/N blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass, and about 20 vol. % C/A blendstock derived from pyrolysis processing of coal tar fraction. In embodiments, I/N-C/A fuel comprises about 30 vol. % C/A blendstock derived from pyrolysis processing of a high cycloparaffin-content material derived from oil shale or oil sand feedstock. In embodiments, I/N-C/A fuel comprises about 70 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock and about 30 vol. % C/A blendstock derived from pyrolysis processing of a high cycloparaffin-content material derived from an oil shale or oil sand feedstock. 
     In another embodiment of the invention, shown in  FIG. 3 , direct liquefaction  220  of liquefaction feedstock  210  is used to produce C/A blendstock. Liquefaction feedstock  210  may comprise, for example, coal and/or biomass. There are two basic procedures: hydroliquefaction and solvent extraction. In hydroliquefaction, coal  210  is mixed with recycled coal oil  230  and, together with hydrogen  240 , fed to high-pressure catalytic reactor  220  where hydrogenation of coal  210  takes place. In solvent extraction, also termed “solvent refining,” coal  210  and hydrogen  240  are dissolved at high pressure in a recycled coal-derived solvent  230  which transfers hydrogen  240  to coal  210 . After phase separation  260 , wherein gases  270  and ash  280  may be removed from coal liquid  250  which may be further cleaned and upgraded by refinery procedures, liquid fuels  290  are produced. In solvent refining, with a low level of hydrogen transfer, a solid, relatively clean fuel termed “solvent refined coal”  290  is obtained. As in pyrolysis, the compounds are similar to the coal tars and highly aromatic in nature. Hydrogenation and selective catalytic processing, as known to one of skill in the art, may be performed to yield a mix of cycloalkanes and aromatics that provide the C/A blendstock. 
     In embodiments, the I/N-C/A fuel comprises about 20 vol. % C/A blendstock derived from direct liquefaction of a coal feedstock. In embodiments, the I/N-C/A fuel comprises about 80 vol. % I/N blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass, and about 20 vol. % C/A blendstock derived from direct liquefaction of a coal feedstock. 
     In an embodiment, C/A blendstock comprises cycloalkanes obtained by separation (e.g., via distillation or extraction) of cycloalkanes selected from the group consisting of C9-C15 cycloalkanes from petroleum feedstocks. In embodiments, C/A blendstock comprises aromatic compounds obtained by separation (e.g., via distillation or extraction) of aromatic compounds selected from the group consisting of C9-C15 single-ring aromatic compounds from petroleum feedstocks. Suitable petroleum feedstocks comprise oil sand- and/or oil shale-derived products that are inherently rich in cycloalkanes. 
     In an embodiment, C/A blendstock is produced by catalytic cyclization and/or reforming of I/N blendstock prepared from triglyceride and/or fatty acid feedstocks as disclosed hereinabove. In this embodiment, I/N blendstock may be produced via: (1) catalytic triglyceride dissociation into fatty acids and glycerol, (2) glycerol removal, (3) oxygen removal from fatty acids (via catalytic decarboxylation and/or reduction) to yield normal paraffins, and, to the extent desired, (4) catalytic isomerization of a portion of these normal paraffins to yield isoparaffins. In embodiments, I/N-C/A fuel comprises about 35 vol. % C/A blendstock derived from catalytic processing of triglyceride feedstock. In embodiments, I/N-C/A fuel comprises about 65 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock and about 35 vol. % C/A blendstock derived from catalytic processing of triglyceride feedstock. 
     In another embodiment of the invention, C/A blendstock is produced from biomass-derived lignin feedstock. C/A blendstock may be produced via catalytic depolymerization of biomass-derived lignin feedstock followed by hydroprocessing as required to yield a desired proportion (for example, JP-8-quality) of cycloalkanes and aromatics. In embodiments, the I/N-C/A fuel comprises about 20 vol. % C/A blendstock derived from pyrolysis of biomass-derived lignin. In alternative embodiments, I/N-C/A fuel comprises about 15 vol. % C/A blendstock derived from catalytic processing of lignin. In embodiments, I/N-C/A fuel comprises about 80 vol. % I/N blendstock derived from Fischer-Tropsch processing of natural gas, coal, and/or biomass, and about 20 vol. % C/A blendstock derived from pyrolysis processing of biomass-derived lignin. In embodiments, I/N-C/A fuel comprises about 85 vol. % I/N blendstock derived from catalytic processing of triglyceride feedstock and about 15 vol. % C/A blendstock derived from catalytic processing of lignin. 
     V. I/N-C/A Fuel 
     A finished I/N-C/A fuel may have “drop-in compatibility” with its petroleum-derived counterpart, i.e. the I/N-C/A fuel may be blended in any proportion, from 0 vol. % to 100 vol. % with a petroleum-derived counterpart. The disclosed I/N-C/A fuel provides for the blending of fuel components (including isoparaffins, normal paraffins, cycloalkanes, and/or aromatics), at least two of which are derived from disparate processes, to create UN-C/A fuel. In embodiments, at least 50 weight percent of an aviation-grade UN-C/A kerosene fuel is derived from coal, natural gas, or a combination thereof. In embodiments, at least 50 weight percent of an I/N-C/A fuel is derived from biomass. In embodiments, at least 10 weight percent of an I/N-C/A fuel is derived from non-cracked bio-oil. In embodiments, UN-C/A fuel has a cetane number of greater than about 70. 
     In embodiments, the I/N-C/A fuel complies with specifications for Jet A and/or another civilian jet fuel. In embodiments, the I/N-C/A fuel complies with a military jet fuel specification selected from JP-8 and other military-grade jet fuel specifications. 
     In addition to meeting fuel property and performance requirements listed in U.S. military and ASTM (American Society for Testing and Materials) International aviation jet fuel specifications, in embodiments, an I/N-C/A-blended fuel will also meet applicable U.S. military-specified fit-for-purpose requirements that address a variety of fuel performance and materials compatibility issues. As mentioned hereinabove, fit-for-purpose requirements refers to fuel property requirements that are not necessarily addressed by military or ASTM standards, but are important to fuel performance and stability in jet engines and during fuel handling, distribution, and storage. Examples of fit-for-purpose requirements include fuel compatibility with aircraft fuel and engine system materials of construction, adequate fuel performance in compression ignition (versus turbine) engines in a wide variety of ground environments, and possible fuel performance requirements related to swelling of elastomeric seals in, for example, turbine engines. These fit for purpose requirements, in addition to feedstock properties and ASTM standards are used to determine the optimal ratio of the I/N blendstock to the C/A blendstock. 
     VI. EXAMPLES 
     Example 1 
     Fuel Sample A 
     A FT fuel produced from natural gas and containing iso-paraffinic and normal paraffin hydrocarbons did not comply with density requirement of the JP-8 military specification (MIL-DTL-83133E). In this example, a mixture of aromatic hydrocarbon fluid containing aromatic hydrocarbons ranging in carbon chain length from 8-16, was blended to a concentration of 23% by weight with the FT fuel. A summary of results from Fuel Sample A compared to specification requirements outlined in MIL-DTL-83133E is provided in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Results from Jet Fuel Specification Tests of 
               
               
                 Fuel Sample A Comprising Blend of Aromatic Hydrocarbon 
               
               
                 and Fischer-Tropsch Derived Fuel 
               
            
           
           
               
               
               
            
               
                 Specification Test 
                 Sample A 
                 Military Spec 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Acid Number, mg KOH/gm 
                 0.003 
                 0.015 
                 max 
               
               
                 Aromatics, vol % 
                 19.4 
                 25 
                 vol % max 
               
               
                 Olefins, vol % 
                 0.0 
                 5 
                 vol % max 
               
               
                 Sulfur, mass % 
                 0.0 
                 0.30 
                 max 
               
            
           
           
               
               
               
            
               
                 Heat of Combustion, Btu/lb 
                 18500 
                 18400 
               
            
           
           
               
               
               
               
            
               
                 Distillation: 
                   
                   
                   
               
               
                 10% recovered, ° C. 
                 172 
                 205 
                 max 
               
               
                 Endpoint, ° C. 
                 274 
                 300 
                 max 
               
               
                 Residue, vol % 
                 1.4 
                 1.5 
                 max 
               
               
                 Loss, vol % 
                 0.4 
                 1.5 
                 max 
               
            
           
           
               
               
               
            
               
                 Flash Point, ° C. 
                 48 
                  &gt;38 
               
            
           
           
               
               
               
               
            
               
                 Freeze Point, ° C. 
                 −57 
                 −47 
                 max 
               
               
                 Hydrogen Content, mass % 
                 14.0 
                 13.4 
                 min 
               
            
           
           
               
               
               
            
               
                 API Gravity @ 60° F. 
                 48.2 
                 37.0-51.0 
               
               
                 Specific Gravity @ 15° C., g/mL 
                 0.787 
                 0.775-0.84  
               
               
                   
               
            
           
         
       
     
     As seen in the data presented in Table 2, the resulting fuel had a density of 0.788 g/mL achieving the minimum specification requirement of 0.775 g/mL as defined by MIL-DTL-83133E while complying with all of the parameters contained within the specification. Data from gas chromatography of Sample A and a typical FT fuel is provided in  FIG. 4 . 
     Example 2 
     Fuel Sample B 
     The same FT fuel as used in Example 1 was blended at 82% wt. with 8% wt. of a mixed aromatic fluid and 10% wt. cycloparaffinic fluid. A summary of Fuel Sample B results from key specification parameters is provided in Table 5. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Results for Key Jet Fuel Specification Tests of Fuel Sample B Comprising Blend 
               
               
                 of Aromatic and Cycloparaffin Hydrocarbons with Fischer-Tropsch Derived Fuel 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Specific 
                 Freeze 
                 Flash 
                 HHV, 
                   
               
               
                   
                 Gravity, g/mL 
                 Point,° C. 
                 Point, ° C. 
                 MJ/kg 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Mil Spec 
                 0.775-0.84 
                 −47 
                 &gt;38 C. 
                 &gt;42.8 
                 Specification value is 
               
               
                   
                   
                   
                   
                   
                 a lower heating value 
               
               
                 Sample B 
                 0.779 
                 −61.4 
                 48 
                 46.1 
                 Lab analysis 
               
               
                 FT Fuel 
                 0.755 
                 −56.7 
                 48 
                 46.6 
                 Lab analysis 
               
               
                   
               
            
           
         
       
     
     As seen in the results in Table 5, the resulting fuel Sample B possessed a MIL-DTL-83133 E specification compliant fuel with a density of 0.779 g/mL. 
     Example 3 
     Fuel Sample C 
     Two hydrocarbon blendstocks, one consisting of normal- and iso-paraffinic hydrocarbon and the second consisting of a mixture of aromatic and cycloparaffinic hydrocarbons, were produced exclusively from crop oil and blended to achieve a fuel sample complying with the requirements of MIL-DTL-83133E. In this example, neither fuel blendstock possessed, on its own, the physical characteristics required by the specification; however, through blending at a ratio of 44% normal and iso-paraffinic blendstock, and 66% aromatic and cycloparaffinic blendstock, the resulting fuel achieved the necessary characteristics. A summary of results from Fuel Sample C compared to specification parameters outlined in MIL-DTL-83133E is provided in Table 6. Data from gas chromatography of Sample C and a typical JP-8 fuel is provided in  FIG. 5 . 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Results from Jet Fuel Specification Tests of Fuel 
               
               
                 Sample C Comprising a Blend of Two Discrete Hydrocarbon 
               
               
                 Blendstocks Produced from Crop Oil 
               
            
           
           
               
               
               
            
               
                 Specification Test 
                 Sample C 
                 Military Spec 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Aromatics, vol % 
                 19.8 
                 25 
                 vol % max 
               
               
                 Olefins, vol % 
                 1.9 
                 5 
                 vol % max 
               
            
           
           
               
               
               
            
               
                 Heat of Combustion, Btu/lb 
                 18400 
                 18400 
               
            
           
           
               
               
               
               
            
               
                 Distillation: 
                   
                   
                   
               
               
                 10% recovered, ° C. 
                 171 
                 205 
                 max 
               
               
                 Endpoint, ° C. 
                 255 
                 300 
                 max 
               
               
                 Residue, vol % 
                 1.2 
                 1.5 
                 max 
               
               
                 Loss, vol % 
                 0.4 
                 1.5 
                 max 
               
            
           
           
               
               
               
            
               
                 Flash Point, ° C. 
                 49 
                  &gt;38 
               
            
           
           
               
               
               
               
            
               
                 Freeze Point, ° C. 
                 −52 
                 −47 
                 max 
               
            
           
           
               
               
               
            
               
                 API Gravity @ 60° F. 
                 44.3 
                 37.0-51.0 
               
               
                 Specific Gravity @ 15° C., g/mL 
                 0.805 
                 0.775-0.84  
               
               
                   
               
            
           
         
       
     
     While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Use of the term “optionally” with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc. 
     Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are a further description and are an addition to the preferred embodiments of the present invention. The discussion of a reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent they provide exemplary, procedural or other details supplementary to those set forth herein.