AU2007329380A1

AU2007329380A1 - Fischer-Tropsch derived diesel fuel and process for making same

Info

Publication number: AU2007329380A1
Application number: AU2007329380A
Authority: AU
Inventors: Dennis J. O'rear
Original assignee: Chevron USA Inc
Current assignee: Chevron USA Inc
Priority date: 2006-12-04
Filing date: 2007-12-04
Publication date: 2008-06-12
Also published as: CN101679883A; WO2008070677A1; US20080155889A1; JP2010522249A; ZA200903686B; GB2457190A; GB0909228D0

Description

WO 2008/070677 PCT/US2007/086401 1 FISCHER-TROPSCH DERIVED DIESEL FUEL AND PROCESS FOR MAKING SAME FIELD OF THE INVENTION 5 The invention relates to a Fischer-Tropsch diesel fuel, distillate fuel, or blend component which also meets the specifications for diesel fuel but with a lighter density than conventional diesel fuel and a process for preparing the fuel. 10 BACKGROUND OF THE INVENTION A distillate fuel refers to a fuel containing components boiling above the typical end point of gasoline (approximately 400*F or 204*C), but excludes non-distillable components (material boiling above II 00*F or 593*C). Distillate fuels can be burned 15 in stationary engines, such as those used to generate electricity. A diesel fuel refers to a distillate which may be burned in a diesel engine to provide power for various human activities. The specifications for diesel fuel are more stringent than distillate fuels. For example in the United States, the end point specification for diesel fuels are 640*F (338*C) for No. 2-D and 550*F (288*C) for No. l-D. 20 Various grades of diesel fuel have specifications which place limits on the cloud point. These frequently vary by geographical region and time of year. For example, ASTM D975-00 defines the specifications for No. 1 -D and No. 2-D diesel fuels in the United States. It includes the statement in footnotej of Table 1, "Tenth percentile 25 minimum air temperatures for U.S. locations are provided in Appendix X4-as a means of estimating expected regional temperatures. This guidance is general. Some equipment designs or operations may allow higher or require lower cloud point fuels." The temperatures in Appendix X4 range from a low of -49*C for the northern region of Alaska in January, to +14*C for southern Florida in October. Likewise the 30 World Wide Fuel Charter (2002) includes the statement that the cloud point "maximum must be equal to or lower than the lowest expected ambient temperature." Thus acceptable diesel fuels should have cloud points at or below +14*C, for example, at or below 0*C, or at or below - I 5*C, or at or below -25*C, or at or below -49"C.

WO 2008/070677 PCT/US2007/086401 2 Because their composition will be highly paraffinic, their densities may be below specifications. Where the specification density of conventional diesel fuel needs to be maintained, these compositions of the invention are best used as blend stocks. 5 The Fischer-Tropsch process provides a way to convert a variety of hydrocarbonaceous resources into products usually provided by petroleum. These include diesel fuel. In preparing hydrocarbons via the Fischer-Tropsch process, a hydrocarbonaceous resource, such as, for example, natural gas, coal, refinery fuel gas, 10 tar sands, oil shale, municipal waste, agricultural waste, forestry waste, wood, shale oil, bitumen, crude oil, and fractions from crude oil, is first converted into synthesis gas which is a mixture comprising carbon monoxide and hydrogen. Synthesis gas generation process is one that converts a hydrocarbonaceous asset into 15 synthesis gas by use of a gaseous oxidant. The gaseous oxidant can be purified 02, enriched air, air, steam, carbon dioxide and combinations. The process can either be above ground or in-situ. Examples of above ground. synthesis gas generation processes that use gaseous hydrocarbons having carbons numbers less than 20 (for example methane) as feedstocks for the reactor are AutoThermal Reformer 20 (ATR), Partial Oxidation (POX), Gas Heater Reformer (GH R), and steam reforming. When these feedstocks contain more than 2 mol% C 2 and heavier hydrocarbons, a pre-converter (pre-reformer) is often used to convert the C 2 + hydrocarbons into methane. The pre-reformer uses a catalyst containing a Group VIII metal catalyst (for example Ni) with hydrogen at super-atmospheric pressures. An example of 25 synthesis gas production is described in Kirk Othmer On-Line Edition "Fuels, Synthetic, Liquid Fuels" especially section 1, pages 2 to 14 online Edition incorporated herein by reference. And in the same on-line reference "Methanol 4. Manufacture and Processing" at 30 pages 299 to 311, incorporated herein by reference. Synthesis gas can also be generated by reacting underground hydrocarbonaceous assets with a gaseous oxidant. An example of this in-situ process is described in WO 2008/070677 PCT/US2007/086401 3 U.S. Patent 6,698,515, issued March 2, 2004 to Karanikas et al. Examples of underground hydrocarbonaceous assets are coal, oil shale, heavy oil, tar sands, petroleum deposits and bitumen. An example of a petroleum deposit suitable for in-situ conversion is a petroleum deposit from which the easily-extractable petroleum 5 has been extracted by conventional methods such as pumping, steam flooding, and water flooding. The synthesis gas, in turn, is converted into synthetic hydrocarbonaceous compounds that have a predominantly linear structure, primarily n-paraffins, 1-alcohols, 1 -olefins, 10 and traces of other species. These hydrocarbonaceous species may be refined into various products, including distillate fuels. European Patent Nos. 0861311, 0885275; U.S. Patent Nos. 5689031, 6274029, 6296757, 6607568, 6822131 describe the preparation of a Fischer-Tropsch derived 15 product containing C 5

-C

2 4 primary linear alcohols and preferably primary linear alcohols C12-C24 or C12+ primary linear alcohols. Exactly what primary linear alcohols are supposed to encompass is unclear. However, these middle distillates have a density less than diesel fuel specification. The presence of alcohols are claimed to improve the lubricity of the middle distillate fuel. Unfortunately, the compositions 20 taught in these documents employing the range of alcohols specified, particularly with CII plus alcohols, would fail to meet the cloud point specifications for diesel fuel., and, consequently, they would not be suitable as commercial diesel fuel. The present invention comes from the realization that the alcohols must be CIo and lower and is particularly directed to Fischer-Tropsch derived diesel fuel compositions which are 25 able to meet the cloud point, preferably, enhancing yields in the process. Cloud point represents the temperature below which solid hydrocarbons may form in diesel fuels. Cloud point is determined by ASTM D 2500 which measures the fuel temperature at which solid hydrocarbon crystals formed on cooling. 30 As used in this disclosure the phrase "Fischer-Tropsch derived" refers to a hydrocarbon stream in which a substantial portion, except for added hydrogen, is derived from a Fischer-Tropsch process regardless of subsequent processing steps, WO 2008/070677 PCT/US2007/086401 4 and regardless of the methods of making the synthesis gas. The feed for the creation of the "Fischer Tropsch derived" refers to products derived from any carbon source, for example natural gas, coal, refinery fuel gas, tar sands; oil shale, municipal waste, agricultural waste, forestry waste, wood, shale oil, bitumen, crude oil, and fractions 5 from crude oil. As used in this disclosure the word "comprises" or "comprising" is intended as an open-ended transition meaning the inclusion of the named elements, but not necessarily excluding other unnamed elements. The phrase "consists essentially of" or 10 "consisting essentially of' is intended to mean the exclusion of other elements of any essential significance to the composition. The phrase "consisting of" or "consists of' are intended as a transition meaning the exclusion of all but the recited elements with the exception of only minor traces of impurities. 15 SUMMARY OF THE INVENTION The present invention is directed to a Fischer-Tropsch derived distillate suitable for use as a diesel fuel having a flash point of 38*C minimum measured by ASTM D 93 and a cloud point of+14*C or less and further containing not less than 0.01 wt.% 20 oxygen in at least two 1-alcohols of 1 -pentanol, 1 -hexanol, 1 -heptanol, I -octanol, I-nonanol, and 1-decanol and not more than 0.01 wt.% oxygen in C, . linear alcohols. Mixtures of all the C s- C jo alcohols are within the scope of the invention. The upper wt.% oxygen limit of the alcohols is less than an amount which has the fuel failing the appropriate cloud point and/or other fuel specifications. Optionally two of the three 25 alcohols can be used in a concentration not less than 0.03 wt.% oxygen for the two species, i.e., CS and C7 or C 5 and C6 or C6 and C7. The Fischer-Tropsch derived distillate fuel will have a cloud point of +14"C or less, for example, at or below 0*C, or at or below -15*C, or at or below -25"C, or at or below -49*C. All the wt.% oxygen amounts are on a water free basis. Where density forms part of the diesel fuel 30 specification, Fischer-Tropsche diesels will contain supplements to reach the appropriate density specification.

WO 2008/070677 PCT/US2007/086401 5 It is useful to summarize the boiling points of various paraffins and alcohols; Boiling Point of Boiling Point of Melting Point of Melting Point of Carbon the n-Paraffin the 1-Alcohol the n-Paraffin the I-Alcohol Number (F, "C) ("F, *C) (*F, *C) (*F, 0) 5 97,36 281, 138 -201, -130 -l10,-79 8 258, 125 381, 193 -71, -56 +2,-17 10 346, 174 441,227 -23,-30 +45,+7 11 384, 195 469,242 -14,-25 +61,+16 12 422,216 495,257 114,-10 +79,+26 14 489,254 545,285 +42,+6 +103,39 5 To achieve a flash point by ASTM D 93 of 38*C requires that the boiling point be 250"F (12 *C) or higher. Because of the different boiling points of the paraffins and alcohols, this corresponds to n-Cs and 1-pentanol. Likewise if Co 1 . alcohols are to be excluded, by use of distillation, and they boil at or above 495*F (257*C), then this corresponds to paraffins boiling at above n-C 1 4 eg, Cls,products. The 640*F (338*C) 10 end point of No. 2-D diesel fuel is met when the paraffins are less than or equal to C20. Some branched paraffins up to C24 can be included. The 550*F (288*C) end point of No. l-D diesel fuel is met when the paraffins are less than or equal to C16, although some branched paraffins up to C can be included. When alcohols are added from a source other than the FT reation stream products, the cut point can be higher because 15 the deleterious higher alcohols are not present. The present invention is also directed to a process for preparing a Fischer-Tropsch derived distillate fuel preferably maximizing yield by permitting the CIs... products to be upgraded and retaining the C 1 4 . products with alcohols in the lighter fraction. The 20 process comprises (a) separating a Fischer-Tropsch condensate into a first and second fraction, wherein (i) said first fraction comprises not less than 0.01 wt.% oxygen from at least two of I-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1 -decanol and not more than 0.01 wt.% oxygen in C1, linear alcohols and (ii) said second fraction comprises CI+ linear alcohols; (b) removing the C 1+ linear alcohols from at 25 least a portion of said heavy third fraction and recovering a treated heavy fraction substantially free of C,1+ linear alcohols; and (c) blending at least a portion of the first fraction of step a(i) and a portion of the treated heavy fraction of step (b) in the proper WO 2008/070677 PCT/US2007/086401 6 proportion to prepare a Fischer-Tropsch derived distillate fuel wherein the sum of the oxygenate content of the Cs-Cio alcohols present are within the range of from 0.01 wt.% oxygen and I wt.% oxygen, the cloud point is not more than +14*C, and the flash point of 380C minimum measured by ASTM D 93. This flash point can 5 generally be met where 121*C (250*F) is the minimum 5% point measured by ASTM D 2887. In carrying out the process of the invention a third fraction may be separated from the Fischer-Tropsch condensate in step (a) which contains C4. linear alcohols. 10 The present invention resides in the discovery that the presence of more than 0.01 wt.% oxygen in C1+ linear alcohols will significantly increase the cloud point of the composition rendering it unsuitable for use as a diesel fuel. Further processing the Cis, fraction also can increase the yields since C14. paraffins are suitable for use in diesel fuel. As used in this disclosure, the term "C4. linear alcohols" refers to linear 15 alcohols containing 4 or less carbon atoms in the molecule, such as methanol, ethanol. 1-butanol, and 1-propanol. The term "Cn. linear alcohols" refers to linear alcohols having I I or more carbon atoms in the molecule, such as I -undecanol, I -dodecanol, 1 -tridecanol, 1 -tetradecanol, 1 -pentadecanol, 1 -hexadecanol, etc. Linear C5-Cio alcohols referred to in this disclosure are 1-pentanol, 1-hexanol, 1-heptanol, I -octanol, 20 1 -nonanol, and 1 -decanol, and mixtures of these. DETAILED DESCRIPTION OF THE INVENTlON The present invention is based upon the discovery that the presence of as little as 25 0.0 1 wt.% oxygen in Cm linear alcohols in a Fischer-Tropsch derived distillate fuel will raise the cloud point to an unacceptable temperature. Surprisingly, the presence of C5-Cio linear I -alcohols, more specifically I -pentanol, 1-hexanol, I -heptanol, 1-octanol, 1-nonanol, and 1-decanol in the same fuel has a negligible effect on cloud point. Minor other alcohols species and higher carbon number alcohols can be 30 included so long as the diesel fuel cloud point specifications are met. This generally means other alcohol species would be present only as impurities. Additionally the problem to be solved was to reduce the cost of preparation of diesel fuel by reducing WO 2008/070677 PCT/US2007/086401 7 the severity of the hydrotreating operation which increases yield while meeting the cloud point requirements for diesel fuel. In the process of the invention the Fischer-Tropsch product (condensate, wax or 5 blends) is separated into at least two fractions, a first fraction comprising CIO and lower alcohols and a heavier fraction. Preferably the lighter fraction has not less than 0.01 wt.% oxygen of at least two of 1 -pentanol, I -hexanol, I -heptanol, I -octanol, 1-nonanol, and 1-decanol and not more than 0.01 wt.% oxygen in Cn. linear alcohols and a second heavier fraction comprising C 1. linear alcohols. A portion of the 10 heavier second fraction which is intended to be blended back into the first fraction is treated to remove substantially all of the C 1 I. linear alcohols present. Finally, the treated heavy second fraction is blended with at least a portion of the first fraction in a proportion calculated to yield a Fischer-Tropsch derived distillate fuel having a cloud point of not less than +14*C. In general, the sum of the oxygenate content of the C 5 15 CIO alcohols present the Fischer-Tropsch derived distillate fuel will fall within the range of from 0.01 wt.% oxygen and 1 wt.% oxygen. Combinations of any two alcohols, i.e. Cs and C 6 or Cs and C 7 or C 6 and C 7 can be present in an amount from 0.01 wt.% oxygen, preferably 0.03 wt.% oxygen up to 1.0 wt.% oxygen. The fuel preferably should also have a flash point 38*C minimum measured by ASTM D 93. 20 Unless blended with conventional petroleum feedstocks. the density will be less than the standards but still function effectively as a distillate and diesel fuel. The products recovered from the Fischer-Tropsch operation (condensate, wax and blends) will contain varying amounts of oxygenates. The majority of the oxygenates 25 present are in the form of alcohols; however, lesser amounts of ketones, aldehydes, carboxylic acids, and anhydrides may also be present. In order to prepare the heavy fraction which is substantially free of CI+ linear alcohols, it is necessary to either remove the Cn I+ linear alcohols or convert them into other hydrocarbons. There are a number of processes known to those skilled in the art which may be used to 30 accomplish this step. These processes include, but are not necessarily limited to, hydrotreating, hydrocracking, hydroisumerization, dehydration, adsorption, absorption, or various combinations of these processes. As used in this disclosure, "substantially free of C, , linear alcohols" means that the distillate fraction contains WO 2008/070677 PCT/US2007/086401 8 C, 1 alcohols in an amount less than a concentration which increases the cloud point to values warmer than the diesel fuels specification. Hydrocracking and hydrotreating are similar processes which differ primarily in the 5 degree of severity. They may be referred to collectively in this disclosure as "hydroprocessing". In the process of the present invention hydrocracking and hydrotreating are intended primarily for the purpose of removing alcohols that arc present in the Fischer-Tropsch distillate. "Hydrotreating" refers to a catalytic process, usually carried out in the presence of free hydrogen, in which the primary purpose 10 when used to process conventional petroleum derived feed stocks is the removal of various metal contaminants, such as arsenic; heteroatoms, such as sulfur and nitrogen; and aromatics from the feed stock. In the present process, the primary purpose is to remove the alcohols and secondarily to saturate the olefins present. Generally, in hydrotreating operations cracking of the hydrocarbon molecules, i.e., breaking the 15 larger hydrocarbon molecules into smaller hydrocarbon molecules is minimized. For the purpose of this discussion the term hydrotreating refers to a hydroprocessing operation in which the conversion is 20% or less. Conversion can be defined on the basis of the increase in the amount of material in the-product relative to the feed, boiling below the 5% point of the feed as measured by ASTM D 2887. 20 "Hydrocracking" refers to a catalytic process, usually carried out in the presence of free hydrogen, in which the cracking of the larger hydrocarbon molecules is a primary purpose of the operation. In contrast to hydrotreating, the conversion rate for hydrocracking, for the purpose of this disclosure shall be more than 20%. In the present invention, hydrocracking is used to remove the alcohols and to hydrogenate 25 the olefin. Catalysts used in carrying out hydrotreating and hydrocracking operations are well known in the art. See for example U.S. Patent Nos. 4,347,121 and 4,810,357, the contents of which are hereby incorporated by reference in their entirety, for general 30 descriptions of hydrotreating, hydrocracking, and of typical catalysts used in each of the processes. Suitable catalysts include noble metals from Group VIIIA (according to the 1975 rules of the International Union of Pure and Applied Chemistry), such as platinum or palladium on an alumina or siliceous matrix, and unsulfided Group VIIlA WO 2008/070677 PCT/US2007/086401 9 and Group VIB, such as nickel-molybdenum or nickel-tin on an alumina or siliceous matrix. U.S. Patent No. 3,852,207 describes a suitable noble metal catalyst and mild conditions. Other suitable catalysts are described, for example, in U.S. Patent Nos. 4,157,294 and 3,904,513. The non-noble hydrogenation metals, such as 5 nickel-molybdenum, are usually present in the final catalyst composition as oxides, or more preferably or possibly, as sulfides when such compounds are readily formed from the particular metal. involved. Preferred non-noble metal catalyst compositions contain in excess of 5 wt.% oxygen, preferably 5 to 40 wt.% oxygen molybdenum and/or tungsten, and at least 0.5, and generally I to 15 wt.% oxygen of nickel and/or 10 cobalt determined as the corresponding oxides. Catalysts containing noble metals, such as platinum, contain in excess of 0.01% metal, preferably between 0.1 and 1.0% metal. Combinations of noble metals may also be used, such as mixtures of platinum and palladium. 15 The hydrogenation components can be incorporated into the overall catalyst composition by any one of numerous procedures. The hydrogenation components can be added to matrix component by co-mulling, impregnation, or ion exchange and the Group VI components, i.e.; molybdenum and tungsten can be combined with the refractory oxide by impregnation, co-mulling or co-precipitation. Although these 20 components can be combined with the catalyst matrix as the sulfides, that is generally not prcfcrrcd, as the sulfur compounds can interfere with the Fischer-Tropsch catalysts. The matrix component can be of many types including some that have acidic catalytic 25 activity. Ones that have activity include amorphous silica-alumina or may be a zeolitic or non-zeolitic crystalline molecular sicvc. Examples of suitable matrix molecular sieves include zeolite Y, zeolite X and the so called ultra stable zeolite Y and high structural silica:alumina ratio zeolite Y such as that described in U.S. Patent Nos. 4,401,556; 4,820,402; and 5,059,567. Small crystal size zeolite Y, such as that 30 described in U.S. Patent No. 5,073,530 can also be used. Non-zeolitic molecular sieves which can be used include, for example, silicoaluminophosphates (SAPO), ferroaluminophosphate, titanium aluminophosphate and the various ELAPO molecular sieves described in U.S. Patent No. 4,913,799 and the references cited WO 2008/070677 PCT/US2007/086401 10 therein. Details regarding the preparation of various non-zeolite molecular sieves can be found in U.S. Patent Nos. 5,114,563 (SAPO) and 4,913,799 and the various references cited in U.S. Patent No. 4,913,799. Mesoporous.molecular sieves can also be used, for example the M41S family of materials as described in J. Am. Chem. Soc., 5 114:10834-10843(1992)), MCM-41; U.S. Patent Nos. 5,246,689; 5,198,203; and 5,334,368; and MCM-48 (Kresge et al.. Nature 359:710 (1992)). Suitable matrix materials may also include synthetic or natural substances as well as inorganic materials such as clay, silica and/or metal oxides such as silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-berylia, silica-titania as well as 10 ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia, and silica-magnesia zirconia. The later may he either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be composited with the catalyst include those of the montmorillonite and kaolin families. These clays can 15 be used in the raw state as originally mined or initially subjected to calumniation, acid treatment or chemical modification. In performing the hydrocracking and/or hydrotreating operation, more than one catalyst type may be used in the reactor. The different catalyst types can be separated 20 into layers or mixed. Hydrocracking conditions have been well documented in the literature. In general, the overall LHSV is 0.1 hr-1 to 15.0 hr-I (v/v), preferably from 0.25 hr-1 to 2.5 hr-I. The reaction pressure generally ranges from 500 psig to 3500 psig ( 10.4 MPa to 25 24.2 MPa, preferably from 1500 psig to 5000 psig ( 3.5 MPa to 34.5 MPa). Hydrogen consumption is typically from 500 to 2500 SCF per barrel of feed (89.1 to 445 m3 H2/m3 feed). Temperatures in the reactor will range from 400*F to 950*F (205*C to 510*C), preferably ranging from 650*F to 850*F ( 340 0 C to 455 0 C). 30 Typical hydrotreating conditions vary over a wide range. In general, the overall LHSV is 0.5 to 5.0. The total pressure ranging from 200 psig to 2000 psig. Hydrogen recirculation rates are typically greater than 50 SCF/Bbl, and are preferably between WO 2008/070677 PCT/US2007/086401 11 1000 and 5000 SCF/BbL. Temperatures in the reactor will range from 400*F to 800*F (205"C to 425"C). "Hydroisomerization", also called simply "isomerization", is intended to improve the 5 cold flow properties of the Fischer-Tropsch derived product by the selective addition of branching into the molecular structure. In the present invention, it may also be used to remove the alcohols. Isomerization ideally will achieve high conversion levels of the normal paraffins to iso-paraffins while at the same time minimizing the conversion by cracking. isonerization operations suitable for use with the present 10 invention typically uses a catalyst comprising an acidic component and may optionally contain an active metal component having hydrogenation activity. The acidic component. of the catalysts preferably includes an intermediate pore SAPO, such as SAPO- 11, SAPO-3 1, and SAPO-4 1, with SAPO- 11 being particularly preferred. Intermediate pore zeolites, such as ZSM-22, ZSM-23, SSZ-32, ZSM-35, 15 and ZSM-48, also may be used in carrying out the isomerization. Typical active metals include molybdenum, nickel, vanadium, cobalt, tungsten, zinc, platinum, and palladium. The metals platinum and palladium are especially preferred as the active metals, with platinum most commonly used. 20 The phrase "intermediate pore size", when used herein, refers to an effective pore aperture in the range of from 4.0 to 7.1 Angstrom when the porous inorganic oxide is in the calcined form. Molecular sieves having pore apertures in this range tend to have unique molecular sieving characteristics. Unlike small pore zeolites such as erionite and chabazite, they will allow hydrocarbons having some branching into the 25 molecular sieve void spaces. Unlike larger pore zeolites such as faujasites and mordenites, they are able to differentiate between n-alkancs and slightly branched alkenes, and larger alkanes having, for example, quaternary carbon atoms. See U.S. Patent No. 5,413,695. The term "SAPO" refers to a silicoaluminophosphate molecular sieve such as described in U.S. Patent Nos. 4,440,871 and 5,208,005. 30 In preparing those catalysts containing a non-zcolitic molecular sieve and having an hydrogenation component, it is usually preferred that the metal be deposited on the catalyst using a non-aqueous method. Non-zeolitic molecular sieves include WO 2008/070677 PCT/US2007/086401 12 tetrahedrally-coordinated [A102 and P021 oxide units which may optionally include silica. See U.S. Patent No. 5,514,362. Catalysts containing non-zeolitic molecular sieves, particularly catalysts containing SAPO's, on which the metal has been deposited using a non-aqueous method have shown greater selectivity and activity 5 than those catalysts which have used an aqueous method to deposit the active metal. The non-aqueous deposition of active metals on non-zeolitic molecular sieves is taught in U.S. Patent No. 5,939,349. In general, the process involves dissolving a compound of the active metal in a non-aqueous, non-reactive solvent and depositing it on the molecular sieve by ion exchange or impregnation. 10 The dehydration of alcohols may be accomplished by processing the feedstock over a catalyst, such as gamma alumina. During dehydration the alcohols are converted into olefins. The dehydration of alcohols to olefins is discussed in Chapter 5, "Dehydration" in Cataly/ic Processes and Proven Catalysts by Charles L. Thomas, 15 Academic Press, 1970. Another process is disclosed and completely incorporated herein by reference in U.S. Patent No. 6,933,323. Another method, also described in examples of U.S. Patent No. 6,933,323, for removing the alcohols involves passing the condensate through an adsorption bed 20 containing an adsorbent capable of adsorbing the alcohols. A satisfactory adsorbent may include a molecular sieve having low silica to alumina ratio. Large pore molecular sieves having a low silica to alumina ratio, particularly those molecular sieves characterized as having an FAU type of framework, are generally suitable for use as an adsorbent for alcohols and other oxygenates. Preferred FAU molecular 25 sieves are X zenliteswith 13X zeolite being particularly preferred. As used herein, the term "FAU molecular sieve" refers to the IZA Structure Commission standard which includes both X and Y zeolites. The synthesis of X-type zeolites is described in U.S. Patent Nos. 2,882,244; 30 3,685,963; 5,370,879; 3,789,107 and 4,007,253 which are hereby incorporated herein by reference in their entirety. 13X Zeolite are a faujasite (FAU) type X zeolite. It has a low silica/alumina ratio and is comprised of silicon, aluminum and oxygen. The oxygen ring provides a cavity opening of 7.4 angstroms, but can adsorb molecules up WO 2008/070677 PCT/US2007/086401 13 to 10 angstroms. 13X zeolite have a Chemical Abstracts (CAS) number of [63231-69-6]. 13X zeolite arc commercially available from several sources, including Aldrich Chemical Company and the Davison Division of W. R. Grace. Additionally the process as described in U.S. Patent No. 6,933,323 can be used herein as noted 5 above. Flash point is the temperature to which the fuel must be heated to create sufficient fuel vapor above the surface of the liquid fuel for ignition to.occur when exposed to an open flame. Flash point determined by ASTM D 93 and preferably is a minimum 10 of 38*C. The following examples highlight the problem to be solved by the realization of the effect of including C, 1 + alcohols in distillate fuel and not being able to meet diesel cloud point specifications. 15 EXAMPLE I In this example, a 600"F (315*F) end point (by ASTM D2887) Fischer Tropsch diesel fuel with a high i/n ratio was prepared and tested. 20 A commercial sample of Fischer Tropsch C8 0 wax was obtained from Moore and Munger Co. It has an initial boiling point as determined by ASTM D 2887 of 790*F and a boiling point at 5 wt.% of 856 0 F. It was hydrocracked in a single stage pilot plant at 669*F, 1.0 LHSV, 1000 psig, 10000 SCF/Bbl Hydrogen at 90% 25 conversion in a once-through operation (without recycle). A commercial sulfided hydrocracking catalyst was used. A 260-600"F product with the following properties was recovered by distillation. This product contains over 2 wt.% n-C] 4 + n-paraffins yet has a cloud point of -51*C.

WO 2008/070677 PCT/US2007/086401 14 Density at I 5C, g/ml 0.7626 Sulfur, ppm 0 Viscosity at -20*C, cSt 6.382 Freeze Point, uC -47.7 5 Cloud Point, *C -51. Flash Point, *C 54. Smoke Point, mm >45 10 Hydrocarbon types, wt.% by Mass Spec (ASTM D 2789) Paraffins 93.1 Mono-cycloparaffins 5.2 Di-cycloparaffins 1.5 Alkylbenzenes 0.1 15 Benzonaphthalenes 0.0 Naphthalcnes 0.1 N-paraffin Analysis by GC CARBON DISTRIBUTION NORMAL NON NUMBER (Wt. Percent) PARAFFIN N-PARAFFIN 6 0.00 0.00 0.00 7 0.00 0.00 0.00 8 0.12 0.10 0.02 9 8.75 1.83 6.92 10 10.95 1.56 9.39 11 11.25 1.22 10.03 12 11.24 1.19 10.05 13 11.26 0.68 10.58 14 10.66 0.77 9.90 .15 10.21 0.58 9.62 16 9.70 0.41 9.29 17 9.37 0.30 9.07 18 6.36 0.03 6.33 19 0.12 0.00 0.12 20 0.02 0.00 0.02 21 0.00 0.00 0.00 22-52 0.00 0.00 0.00 TOTAL 100.00 8.67 91.33 Average Carbon Number: 13.28 Average Molecular Weight: 187.93 20 WO 2008/070677 PCT/US2007/086401 15 Simulated Distillation, *F by wt.%, ASTM D 2887 0.5% 267 5% 287 10% 310 5 20% 342 30% 378 40% 405 50% 439 60% 472 10 70% 504 80% 535 90% 564 95% 579 99% 595 15 99.5% 598 This sample was mixed with n-dodecanol in varying amounts and the cloud point was determined. The original sample had a cloud point of -5 1C, which meets the most 20 stringent cloud point specification in ASTM D975, but adding as little as 0.1 wt% oxygen as dodecanol significantly increased the cloud point.

WO 2008/070677 PCT/US2007/086401 16 u -, CCc 000 0--- LC & F-: 20~ C -Z 4C) 0~0 00 p~C to00 0 4)0 0 WO 2008/070677 PCT/US2007/086401 17 EXAMPLE 2 An additional diesel fuel sample was prepared with a 675*F (357*C) and 450*F (232*C) end points and a moderate i/n ratio and tested as shown below. This sample 5 meets the end point and flash point requirements of ASTM D975 for No., 2-D fuel. Samples of Fischer Tropsch condensate and wax from a cobalt catalyst were obtained. The condensate was hydrotreated at 3.36 LHSV, 1000 psig total pressure, 5000 SCFB recycle gas rate over a sulfided commercial whole extrudate non-acidic NiMo/A 2 0 3 10 catalyst. The wax was hydrocracked at 1.2 LHSV, 66% per pass conversion below 675*F (357*C), 1000 psig total pressure, 5000 SCFB recycle gas rate over a sulfided commercial whole extrudate acidic NiW/A1 2 0 3 -SiO 2 catalyst. The products from the two units were continuously blended and distilled. The material boiling above the diesel cut point (roughly 675*F - 357*C) was recycled to extinction in the 15 hydrocRcker.

WO 2008/070677 PCT/US2007/086401 18 Properties of the 250-675*F (12 1-357*C) diesel fuel are shown below: Gravity, *API 52.7 Nitrogen, ppm 0.24 Sulfur, ppm < I Water, ppm by Karl Fisher, ppm 21.5 Pour Point/Cloud Point/ CFPP, *C / Freeze Point, *C -23 / -18 / -21 / -14 Flash Point, *C 58 Viscosity at 25"C / 40*C, cSt 2.564 / 1.981 Cetane Number 74 Aromatics by Supercritical Fluid Chromatography, wt% < I Neutralization No. 0 Ash Oxide, Wt/o <0.001 Ramsbottom Carbon Residue, wt% 0.02 Cu Strip Corrosion IA Color, ASTM D1500 0 GC-MS Analysis Paraffins, Wt% 100 Paraffin i/n ratio 2.1 Oxygen as oxygenates, ppm <6 Olefins, Wt% 0 Average Carbon Number 15.15 Distillation by D-2887 by Wt%, *F and D-86 by Vol %, *F D-2887 D-86 0.5/5 255/300 329/356 10/20 326/368 366/393 30/40 406/449 419/449 50 487 480 60/70 523/562 510/539 80/90 600/637 567/597 95/99.5 659/705 615/630 WO 2008/070677 PCT/US2007/086401 19 Detailed GC-MS analysis. Formula N-alkane area % Branched alkane area % Total alkanes i/n by Carbon No. C91120 2.96 0.00 2.96 - C10H22 3.59 4.24 7.83 1.18 C1lH24 3.80 4.65 8.45 122 C12H26 3.65 4.77 8.42 1.31 C13H28 3.41 5.34 8.75 1.57 C14H30 3.00 5.34 8.34 1.78 C151H32 2.61 5.56 8.17 2.13 C16H34 2.33 8.65 10.98 3.71 C171136 1.99 5.74 7.72 2.89 C18H38 1.51 6.11 7.62 4.04 C19H40 1.60 5.98 7.58 3.73 C201H42 1.18 5.35 6.53 4.52 C21144 0.58 3.82 4.41 6.54 C22H46 0.22 2.00 2.23 8.94 5 This diesel fuel was mixed with various primary linear alcohols and the cloud point determined. Adding 1-heptanol makes no significant change in the cloud point, but adding CoI . alcohols does increase the cloud point. These results show that a +14"C cloud point cannot be achieved when the C 16 alcohol content is in excess of 0.3 wt% oxygen as oxygenates. Adding I-hexanol does not make a significant increase in the 10 cloud point, but adding 1-dodecanol does. When C 1 + alcohols were present in blends with 1-hexanol, significant increase in the cloud point was still observed in most cases. High levels of 1-hexadecanol and 1-eicosanol were not soluble at ambient conditions (and even 50"C). Thus cloud points could not be measured. They were well in excess of +14 0 C. 15 WO 2008/070677 PCT/US2007/086401 20 0 U 8 E) 00 c) -o 0 cn 0 0 0 C> C) C)C 0 -V 0000 0 ) 00 0 0 0 0) -a 10 " C c c -2 Z: 0 0 0 x 4x ) 0- m -o a 01 WO 2008/070677 PCT/US2007/086401 21 EXAMPLE 3 5 The diesel product from example 2 was further distilled to obtain a 250-400*F (121-204 0 C) diesel fuel fraction which simulated a No. 1-D fuel with these properties. Property Value Units Density @ 20*C 0.7269 g cm" Refractive Index @ 20*C 1.4096 Molecular Weight 142 Daltons n-d-M Analysis % Paraffinic Carbon 98.42 Wt % % Naphthenic Carbon 1.52 Wt % % Aromatic Carbon 0.00 Wt % Naphthenic Rings per molecule 0.03 Aromatic Rings per molecule 0.00 Cloud Point -60 *C Sulfur 2.3 ppm weight Nitrogen 0.178 ppm weight Bromine Index 228 Aromatics by SFC Monoaromatics < 0.5 Wt % Polyaromatics < 0.5 Wt % Total Aromatics < 0.5 Wt % FIAM (D1319) Aromatics I Vol % Olefins 0 Vol % Paraffins/Naphthenes 99 Vol% n-Paraffin Analysis by Carbon Number n-CS 0.01 Wt % n-C 6 0.01 Wt % n-C 7 0.50 Wt % n-Cs 11.13 Wt % n-Cg 16.42 Wt % n-Clo 16.97 Wt % n-C,, 13.59 Wt % n-C1 2 0.46 Wt % n-C,3 and heavier 0.00 Wt % Total Normal Paraffins 59.09 Wt % Distilliation by D-2887, Wt% by *F St 5 wt% 196/256 10/30 wt% 260/304 50 wt% 330 70/90 wt/o 350/388 95/99 wt% 389/406 WO 2008/070677 PCT/US2007/086401 22 These studies show that addition of small amounts of dodecanol has a significant detrimental impact on the cloud point. Adding as little as 0.01 wt.% oxygen as I -dodecanol resulted in cloud points (as measured by ASTM D2500, "C) well in 5 excess of the lowest cloud limit, -49"C. Adding C 5 to CIO alcohols did not result in a notable increase in the cloud point. As noted above all wt.% oxygen concentrations are on a water free basis.

WO 2008/070677 PCT/US2007/086401 23 0 c 0 0 0 'o 00 00 00 r 0. IL , o 0 0 0 C -o 0C gC 0 C ~o 0 00 - 0 00~~t 0000 0 00g 0 C) co CD 0 - ON - 0 060 406 0~) C6u%6 o C) uU. L, 0 U. oeQ C 1 Q\ ON C CC UA 00( - 6% 0 - _q 00 u r-' 00 a r0c 00 Qo C) r_ 0 en 0i 4 n 4.) 0D m. 0 0 CD 4.) a)C

C-

C.).

WO 2008/070677 PCT/US2007/086401 24 This examples illustrate the inability to get low cloud points with normal alcohols such as 1-dodecanol while Cs to CIO normal alcohols can be employed and obtain a low cloud point, especially when the distilled fraction has a lower end point than the prior example and a moderate i/n ratio.

Claims

1-heptanol, 1-octanol, 1-nonanol, 1-decanol; and mixtures of more than two alcohols, and not more than 0.01 wt.% oxygen in Cap. linear alcohols. 10 2. The Fischer-Tropsch derived distillate of claim I wherein the cloud point is 0OC.

3. The Fischer-Tropsch derived distillate of claim 2 wherein the cloud point is -15*C or less. 15

4. The Fischer-Tropsch derived distillate of claim 3 wherein the cloud point is -25*C or less.

5. The Fischer-Tropsch derived distillate of claim 4 wherein the cloud point is 20 -49*C or less.

6. The Fischer-Tropsch derived distillate of claim I wherein the sum of the oxygenate content of the C 5 -Cjo linear alcohols present are within the range of from 0.0 1 wt.% oxygen and I wt.% oxygen. 25

7. A process for preparing a Fischer-Tropsch derived distillate fuel which comprises; (a) separating a Fischer-Tropsch condensate into a first and second 30 fraction, wherein: (i) said first fraction comprises not less than 0.01 wt.% oxygen of alcohols selected from the group consisting of I-pentanol, WO 2008/070677 PCT/US2007/086401 26 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, and mixtures thereof, and not more than 0.01 wt.% oxygen in C, 1 . linear alcohols and 5 (ii) said second fraction comprises C 1 1+ linear alcohols; (b) removing the C 11 + linear alcohols from at least a portion of said second fraction and recovering a treated heavy fraction substantially free of C 1 + linear alcohols; and 10 (c) blending at least a portion of the first fraction of step a(i) and a portion of the treated heavy fraction of-step (b) in the proper proportion to prepare a Fischer-Tropsch derived distillate fuel wherein the sum of the oxygenate content of the Cs-C 0 alcohols present are within the 15 range of from 0.01 wt.% oxygen and to I wt.% oxygen, the cloud point is not more than +14*C, and the flash point 38*C minimum measured by ASTM D 93.

8. The process of claim 7 wherein the first fraction and the second fraction are 20 blended in step (c) with the proper proportion to prepare a Fischer-Tropsch derived distillate fuel having a cloud point of not more than 04C.

9. The process of claim 8 wherein the first fraction and the second fraction are blended in step (c) with the proper proportion to prepare a Fischer-Tropsch 25 derived distillate fuel having a cloud point of not more than -1 5*C.

10. '[he process of claim 7 wherein the Fischer-Tropsch condensate is separated into first, second, and third fractions wherein said first and second fractions are as described and said third fraction comprises C 4 . linear alcohols. 30

11. The process of claim 7 wherein the second fraction is treated by a process selected from hydrotreating, hydrocracking, hydroisomerization, dehydration, WO 2008/070677 PCT/US2007/086401 27 adsorption, absorption, or a combination thereof to obtain the treated heavy fraction substantially free of C I. linear alcohols.

12. In a distillate fuel having a cloud point of+14"C or less, the improvement 5 comprising not less than 0.01 wt.% oxygen in at least two alcohols selected from the group consisting of 1 -pentanol, I -hexanol, 1 -heptanol, 1 -octanol. I -nonanol, 1 -decanol, and mixtures of more than two alcohols; and not more than 0.01 wt.% oxygen in CI14 linear alcohols. 10 13. The distillate fuel of claim 12 wherein the cloud point is 0*C or less.

14. The distillate fuel of claim 13 wherein the cloud point is -15*C or less.

15. The distillate fuel of claim 12 wherein the sum of the oxygenate content of the 15 C 5 -Cio linear alcohols present are within the range of from 0.01 wt.% oxygen and I wt.% oxygen.

16. The diesel fuel of claim 12 wherein the alcohol is any two of the C 5 -CIo linear alcohols in a total concentration less than I wt.% oxygen. 20

17. The Fischer-Tropsch derived distillate of claim I wherein the alcohol is any two of the C 5 -CjO linear alcohols in a total concentration less than I wt.% oxygen. 25 18. The Fischer-Tropsch derived distillate of claim 7 wherein the alcohol is any two of the C 5 -CIO linear alcohols in a total concentration less than I wt.% oxygen.

20. The Fischer-Tropsch derived distillate according to claim 19 with I-alcohols 30 selected from the groups consisting of Cs and C 6 ; Cs and C 7 ; or C 6 and C,.

21. The process of claim 7 wherein the first fraction further includes 1-alcohols Cs, C) and C 1 0 and step b removes the C, 11 linear alcohols from at least a WO 2008/070677 PCT/US2007/086401 28 portion of said second fraction and recovering a treated heavy fraction substantially free of CI linear alcohols and step( c) blends at least a portion of the first fraction of step a(i) and a portion of the treated heavy fraction of step (b). 5

22. The diesel fuel of claim 12 further comprising 1-alcohols selected from the group consisting of C 8 , C 9 and CIO and mixtures thereof alcohols and wherein the paraffins are at least 90% i-paraffins. 10 23. The diesel fuel of claim I further comprising 1-alcohols selected from the group consisting of Cg, C 9 and Clo and mixtures thereof alcohols and wherein the paraffins are at least 90% i-paraffins.