Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
  • C07C2/02—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons
  • C07C2/04—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation
  • C07C2/06—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation of alkenes, i.e. acyclic hydrocarbons having only one carbon-to-carbon double bond
  • C07C2/08—Catalytic processes
  • C07C2/14—Catalytic processes with inorganic acids; with salts or anhydrides of acids
  • C07C2/16—Acids of sulfur; Salts thereof; Sulfur oxides
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
  • C07C5/03—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of non-aromatic carbon-to-carbon double bonds
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G45/00—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G50/00—Production of liquid hydrocarbon mixtures from lower carbon number hydrocarbons, e.g. by oligomerisation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G69/00—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one other conversion process
  • C10G69/02—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one other conversion process plural serial stages only
  • C10G69/12—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one other conversion process plural serial stages only including at least one polymerisation or alkylation step
  • C10G69/126—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one other conversion process plural serial stages only including at least one polymerisation or alkylation step polymerisation, e.g. oligomerisation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/04—Liquid carbonaceous fuels essentially based on blends of hydrocarbons
  • C10L1/08—Liquid carbonaceous fuels essentially based on blends of hydrocarbons for compression ignition
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
  • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
  • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
  • C07C2523/42—Platinum
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2527/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • C07C2527/02—Sulfur, selenium or tellurium; Compounds thereof
  • C07C2527/053—Sulfates or other compounds comprising the anion (SnO3n+1)2-
  • C07C2527/054—Sulfuric acid or other acids with the formula H2Sn03n+1
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/04—Diesel oil

Definitions

• the invention generally relates to turbine and diesel fuels and methods for making the same, and more specifically, methods to convert renewable branched chain olefins including 2- ethyl-l-hexene to fuels suitable for use in turbine and diesel engines.
• FIG. 1 is a GC/MS chromatogram of a dimerized ⁇ -pinene product mixture, according to embodiments of the invention.
• FIG. 2 is a plot of a GC-MS total ion chromatogram for the oligomers produced from 1- butene, according to embodiments of the invention.
• FIG. 3 is a graph of the relative area integration for each of the oligomers by carbon number for the GC-MS chromatogram of Figure 2 above, according to embodiments of the invention.
• FIG. 4 is an ⁇ NMR spectrum of butene oligomers, according to embodiments of the invention.
• FIG. 5 is an ⁇ NMR spectrum of hydrogenated butene oligomers, according to embodiments of the invention.
• FIG. 6 is a Gas Chromatogram of hydrogenated butene oligomers, according to embodiments of the invention.
• FIG. 7 is a Gas Chromatogram of distilled fuel, according to embodiments of the invention.
• FIG. 8 is a H (top) and C (bottom) NMR spectra of the product mixture derived from sulfuric acid dimerization of 2-ethyl-l-hexene, according to embodiments of the invention.
• FIG. 9 is a gas chromatogram (GC) of 2-ethyl-l-hexene dimers, according to embodiments of the invention.
• FIG. 10 is a mass spectrum of a typical hydrogenated 2-ethyl-l-hexene dimer, according to embodiments of the invention.
• Embodiments of the invention generally relate to turbine and diesel fuels and methods for making the same, and more specifically, methods to convert renewable branched chain olefins to fuels suitable for use in turbine and diesel engines.
• Embodiments of the invention generally relate to a process for making fuels including providing an effective amount of one or more branched olefins and adding active heterogeneous acid catalyst(s) to the branched olefins to produce a mixture.
• the process further includes heating the (solvent-free) mixture to greater than about 80°C for a sufficient amount of time which may depend on various conditions, such as temperature and reactants, to produce a dimers/catalyst mixture.
• the catalyst is removed from the dimers/catalyst mixture and a hydrogenation catalyst(s) added to the dimers under a hydrogen atmosphere to produce a mixture of stable fuels.
• the branched olefin(s) can be branched alkenes having from 5-15 carbon atoms, including 2-ethyl-l-hexene.
• the branched olefins can be derived from products produced by fermentation of biomass.
• the branch i.e., the shortest chain can be from 1 to 4 carbons in length, such as 1-2 (methyl, ethyl) or simply one carbons in length.
• the olefin can have more than one branch.
• the branched olefin can be an alpha olefin or can be internally unsaturated.
• the olefin can be monounsaturated or di- or poly-unsaturated.
• the branched olefin mixture can be solvent-free, by which it is meant that the mixture consists only of the branched olefin, catalyst and optionally dimers of the branched olefin. Or, it can be substantially solvent free, by which it is meant that the mixture includes up to 5 wt. %, or up to 1 wt. %, or up to 0.1 wt. % of solvent.
• the step of providing branched olefins further includes a mixture of branched olefins.
• the step of adding active heterogeneous acid catalyst(s) to the branched olefins is performed under a N 2 atmosphere.
• another step further includes the step of purifying the stable fuels by removing short chain branched olefins remaining in the stable fuels.
• the purifying step can include filtration and or distillation.
• At least one branched olefin is a C5-C15 branched olefin such as a C 7 or above, e.g., a Cs branched olefin, such as 2-ethyl-l-hexene.
• the heating step can be performed at a temperature of at least 100°C, such as in the range of from about 1 10°C to about 120°C.
• the catalyst includes a Ziegler-Natta catalyst. In other embodiments, the catalyst further includes a co-catalyst.
• fuels are formed in accordance with the processes described herein. Furthermore, butene oligomer fuels are formed in accordance with the processes herein.
• the catalysts are selected from the group consisting of cation exchange resins, acid clays, zeolites, polyoxometallates, sulfated metal oxides, and other heterogeneous acids.
• the fuels are selected from the group consisting of 5,7-diethyl-5-methylundecane, 8-ethyl-5,6-dimethyldodecane, 6-ethyl-3-methyl-4-propyldecane, 5-ethyl-5,6,7-trimethylundecane, and 5-ethyl-3,5-dimethyl-4-propylnonane and similar molecules, and molecules produced from the coupling of any two structural isomers of 2-ethyl-l-hexene.
• Another aspect of the invention generally relates to a process for making fuels including providing an effective amount of branched olefins including 2-ethyl-l-hexene, adding active heterogeneous acid catalyst(s) to the branched olefins to produce a solvent-free mixture, heating the solvent-free mixture greater than about 80°C for a desired amount of time to produce C[ 6 dimers/catalyst mixture, removing the catalyst(s) from the dimers/catalyst mixture, and adding hydrogenation catalyst(s) to the dimers under hydrogen atmosphere to produce a mixture of stable fuels.
• High density fuel candidates have been synthesized by the present Applicant in up to 90% yield from ⁇ -pinene, a renewable, strained, bicyclic compound derived from wood and plant sources.
• These novel syntheses are based on heterogeneous acidic catalysts (also referred to as heteropolyacidic catalysts) including Montmorillonite- lO and National® NR-50 which promote selective isomerization and dimerization of pinenes under moderate conditions (100°C, atmospheric pressure).
• Montmorillonite clays have been used as catalysts for a number of organic reactions and offer several advantages over classical acids. For example, they are highly acidic, non-corrosive, can be utilized under mild reaction conditions, and typically result in high yields with good selectivity.
• Mesoporous Montmorillonite clays which are dioctahedral phyllosilicates, are composed of hydrated sodium, calcium, aluminum, magnesium, silicate hydroxide (Na,Ca)o.. 3 3(Al,Mg) 2 (Si 4 0io)(OH) 2 - zH 2 0, with an octahedral layer (A10 6 units) sandwiched between two tetrahedral layers (S1O 4 units). Potassium, iron, and other cations are common impurities. These clays typically have a surface area of 220-270 m /g.
• Montmorillonite-KlO is a strong Bronsted and Lewis acidic catalyst shown to be highly active for the dimerization of ⁇ -pinene concomitant with ring opening followed by dehydrogenation to produce p-cymene. Use of this catalyst resulted in a dimer yield of dimer to about 75%.
• National® NR-50 was capable of producing dimers in up to 90% yield but was less active than the acidic clay. Amberlyst-15, a common industrial catalyst had very poor activity and conversion even at 150 °C.
• the dimer mixtures were upgraded through hydrogenation over PtO? and fractional distillation.
• the synthesized fuels have a density of about 0.94 g/cc, and a net volumetric heating value of about 39.5 MJ/L (-141,745 BTU/gal). These values are nearly identical to those of the widely used tactical fuel JP-10 (which is primarily composed of exo-tetrahydrodicyclopentadiene), suggesting that these renewable fuels may have applications for rocket propulsion.
• the dimerization reaction is very exothermic, particularly when MMT- 10 is used as the catalyst. Runaway reactions can occur with both MMT-K10 and Nafion, especially with concentrated solutions or in the absence of a suitable heat sink. Slow addition of ⁇ - pinene to a refluxing reaction mixture at 100 °C was determined to be the safest method of addition.
• the solid acid catalyst 100 mg Nation or 500 mg MMT-K10
• ⁇ -pinene 35 g
• Dimer mixtures were hydrogenated with 1 wt% Pt0 2 under 1-2 psig (about 108-115 kpa) of hydrogen for a period ranging from about 12 hours to about 24 hours. Subsequent distillations were carried out under reduced pressure (4 mm Hg).
• Nafion® NR-50 (Aldrich) was precipitated from a 5% water/alcohol dispersion by addition of dichloromethane (CH 2 C1 2 ) and ether, followed by filtration and drying under vacuum (4 Torr) at ambient temperature (adapted from Kim, T. K.; Kang, M.; Choi, Y. S.; Kim, H. K.; Lee, W.; Chang, H.; Seung, D. J. Power Sources 2007 165, 1-8).
• the MMT-K10 (Aldrich) and dry Amberlyst-15 (Aldrich) were used directly from the bottle.
• a- and ⁇ -pinene have net heats of combustion of 132,300 and 132,500 BTU/gal respectively as calculated based on the experimental heat of formation as reported on http://webbook.nist.gov and by others (Hawkins, J. E.; Eriksen, W. T. J. Am. Chem. Soc. 1954 76, 2669 and Cox, J. D.; Pilcher, G. Thermochemistry of Organic and Organometallic Compounds Academic Press, New York 1970).
• the net heat of combustion of JP-10 is 142,000 BTU/gal (Table 2) (Burdette, G. W.; Lander, H. R.; McCoy, J. R. J. Energy 1978, 2, 289-292).
• both pinene molecules also have positive gas phase heats of formation due to strain energy.
• a path to improving the volumetric heating value of these natural products is selective dimerization that would both increase the density and maintain the ring strain of these molecules.
• Two target dimer molecules are shown in Diagram 1. Semi-empirical calculations for both of these molecules give positive gas phase heats of formation and impressive values for net heat of combustion (based on a density of 0.94 g/mL); 146,900 BTU/gal and 146,500 BTU/gal for the hypothetical hydrogenated a- and ⁇ -pinene dimers, respectively.
• the gas phase data was calculated utilizing MOP AC, while a liquid phase net heat of combustion was calculated assuming a density of 0.94 g/mL and utilizing double the value of the heat of vaporization of ⁇ -pinene according to Hawkins and Armstrong (Hawkins, J. E.; Armstrong, G. T. J. Am. Chem. Soc. 1954 76, 3756). These calculations clearly suggest that dimerized pinenes have the potential to have heating values exceeding that of JP-10.
• Diagram 1 Structures of target dimer molecules and selected calculated properties.
• MMT- 10 was targeted as a catalyst due to its low cost, abundance, and well established reactivity (Madhavan, D.; Murugalakshmi, M.; Lalitha, A.; Pitchumani, K. Catalysis Letters 2001 73, 1).
• MMT-K10 is a layered aluminosilicate functionalized with additional acidic sites through treatment with sulfuric acid. Its acidity can vary several orders of magnitude based on the amount of water present in the sample and it has both Lewis and Bronsted acidic sites (Pillai, S.M.; Ravindranathan, M. J. Chem. Soc. Chem. Commun. 1994 1813-1814).
• the clay can delaminate or separate into particles as little as 1 nm in width and several hundred nanometers in length.
• MMT- 10 Upon addition of MMT- 10 to a flask containing ⁇ -pinene at room temperature, a vigorous reaction occurs, with the catalyst immediately turning red accompanied by a rapid exotherm. Without a heat sink, the reaction rapidly reaches the boiling point of ⁇ -pinene.
• slow addition of ⁇ -pinene to a slurry of the catalyst in heptane at 0 ° C under an inert atmosphere resulted in only a trace amount of isomers (detected by NMR) and no dimers, suggesting that the isomerization reaction is very slow at that temperature.
• the relative ratio of a-pinene:camphene:P- pinene: limonene was 3:5:2:4. Heating the mixture to the reflux temperature of heptane led to a vigorous reaction with production of significant amounts of hydrogen. After 1 h the overall yield of dimer molecules was 80% by GC/MS, with the balance of the product represented by primarily p- cymene, camphene, and tricyclene. Extended heating times at the reflux temperature of heptane did not change the concentration of camphene in the reaction mixture, suggesting that MMT- 10 is a poor catalyst for camphene dimerization. Although camphene represents 35% of the initial isomerized product, it represents only about 10% of the final product mixture.
• the distribution of products was similar to that observed at 100 °C with the addition of about 10% trimer, leading to a 70/10/20 ratio for dimer/trimer/low molecular weight products. This result suggests that the intermediate temperature is ideal, leading to a high conversion to dimer while limiting the formation of trimer or other heavier oligomers.
• the clay catalyst can be removed with some difficulty from the reaction mixture by filtration, however as the catalyst is remarkably well dispersed it was often more convenient to separate the clay by centrifugation followed by decantation.
• This difference in activity may be due to the presence of Lewis acidic sites present in MMT-K10 which may allow for coordination and isomerization of ⁇ -pinene at low temperature (Fernandes, C; Catrinescu, C; Castilho, P.; Russo, P.A.; Carrott, M.R.; Breen, C. Applied Catalysis A 2007 318, 108-120).
• Lewis acidic sites present in MMT-K10 which may allow for coordination and isomerization of ⁇ -pinene at low temperature
• Upon heating to 140 °C for 3 h Upon heating to 140 °C for 3 h, a mixture of primarily ⁇ -pinene and camphene were present with traces of p-cymene and dimer. Given the slow reaction rate, negligible conversion to dimer and high reaction temperature, Amberlyst-15 was not studied in further detail.
• Nafion ® is a sulfonated tetrafluoroethylene based fluoropolymer-copolymer incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (Teflon) backbone, and may be considered to be a perfluorinated sulfonic acid resin.
• Teflon tetrafluoroethylene
• Nafion ® has various chemical configurations and thus several chemical names, including: ethanesulfonyl fluoride, 2-[l-[difluoro- [(trifluoroethenyl)oxy]methyl]- 1 ,2,2,2-tetrafluoroethoxy]- 1 , 1 ,2,2,-tetrafluoro-, with tetrafluoroethylene; and, tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer, for example.
• Nafion ® is insoluble in non-polar solvents.
• the variables x, y, and z are mutually independent integers greater than 1. That is, any one of the variables x, y, z may have an integer value which is not dependent on the value of any other variable.
• MMT- 10 which maintains a high surface area and can delaminate at elevated temperature to yield easily dispersible nanosized catalyst particles
• Nafion does not disperse well in non-polar solvents (Botella, P.; Corma, A.; Lopez-Nieto, J. M. J. Catal. 1999 185, 371-377). This limits the surface area of the catalyst and the relative amount of active sites in contact with the reaction medium.
• Nafion can be well dispersed on inorganic supports including silica or alumina, but the presence of the support can often influence the reactivity and in the case of ⁇ -pinene may lead to more isomerization products and lower ring strain dimers (Kumar, P.; Vermeiren, W.; Dath, J.; Hoelderich, W. F. Energy Fuels 2006 20, 481-487).
• the catalyst was prepared by precipitation of a Nafion dispersion from water/alcohol and was dried under vacuum (4 mmHg) at ambient temperature to yield a flocculent white powder. In a manner similar to Amberlyst-15, Nafion showed virtually no reaction at room temperature for reaction times as long as 24 h.
• the dimer yield varied depending on the catalyst and conditions. Yields of dimer were reduced when MMT-K10 was utilized due to an increase in the amount of p-cym e produced and the inability of MMT-K10 to efficiently homodimerize camphene. The amount of dimer was also heavily influenced by the reaction temperature in that higher temperatures produced trimer molecules and potentially other higher oligomers. Reactions run at greater than 140 °C produced colored solutions ranging from dark yellow to orange-red depending on the reaction time, suggesting that polymeric or conjugated mixtures were being produced. Reactions controlled at about 100 °C with refluxing heptanes gave colorless mixtures when MMT- 10 was utilized as the catalyst and pale yellow mixtures when nation was utilized.
• the net heat of combustion of the dimer mixture was 141,745 BTU/gal, virtually identical to JP-10 (142,000 BTU/gal), while the pour point was determined to be -30 °C, substantially higher than JP-10 with a freezing point of -79 °C.
• the synthetic fuel experiments were initiated using the commercially available precatalyst bis(cyclopentadienyl)zirconium dichloride.
• the precatalyst is activated by treatment with a toluene solution of methylaluminoxane (MAO )followed by removal of the toluene under reduced pressure.
• MAO methylaluminoxane
• the MAO may also be prepared in a solution of any aromatic solvent able to solvate the MAO and the precatalyst such as, without limitation, for example xylene, cumene, and mesitylene.
• coordinating solvents with heteroatoms are not appropriate. Removal of solvent after catalyst activation also removes any residual trimethylaluminum, creating "dried" MAO.
• the "dried" MAO has been shown to have a significant affect on catalyst activity for olefin oligomerization/polyrnerization reactions for several non-metallocene catalysts.
• the MAO is an oligomer of formula [CH 3 A10] n and there is one mole of aluminum for every mole of MAO repeat unit. Similarly, there is one mole of Zr per mole of Cp 2 ZrCl 2 . Conveniently, both the molar ratio of MAO/Cp 2 ZrCl 2 and Al/Zr is 100:1.
• the turnover number (TON) here is at least about 17,000 and may be pushed to as high as on the order of 10 7 whereas the TON achieved by Christoffers and Bergman was only about 10 or less.
• 1-butene (375 mL, about 240 g) is condensed onto CaH 2 and then transferred over the course of 3 h to a chilled (dry ice bath) pressure reaction vessel containing "activated" catalyst. Reactions were performed in a Parr stainless steel pressure reaction vessel lined with a glass insert and stirring was accomplished using a Teflon coated stirring bar.
• the 1-butene [Specialty Gas Concepts, Lancaster, CA, 98% Chemically Pure (CP) grade] was transferred after drying (over CaH 2 ) to the chilled reaction vessel through Tygon tubing. Once the pressure vessel was charged, the port was sealed, the cooling bath was removed, and the reaction vessel was kept at ambient temperature for 16 h (Scheme 7).
• a distillation using a vigreux column is used to remove the C 8 dimer, which accounts for about 25 wt % of the product mixture.
• Roughly 90% of the butene oligomer mixture consists of C 8 dimer and Q 2 , Ci 6 , C 20 , and C 24 oligomers, and there are essentially no oligomers larger than C 32 .
• this fuel contains a mixture of diastereoisomers that are produced as a consequence of the chiral carbon centers (marked with an asterisk in Scheme 7) present at the branch points.
• the diastereoisomers have different physical properties (e.g., boiling point) and can be clearly observed in both the nuclear magnetic resonance (NMR) spectra and GC-MS chromatograms.
• NMR nuclear magnetic resonance
• GC-MS chromatograms.
• the hydrogenated tetramer has three chiral centers.
• the tetramer will have 8 possible stereoisomers. This consists of 4 pairs of enantiomers and 4 different diastereoisomers.
• FIG. 2 is a plot of a GC-MS total ion chromatogram for the oligomers produced from 1-butene (Al/Zr: 100) using the catalyst made by removal of the toluene and delivering the zirconium MAO as a slurry in hydrogenated dimer (3-methyl heptane).
• any lower molecular weight C 4 to about do alkane may be used in place of 3-methy-heptane, such as for example, butane, pentane, hexane, heptane, octane, and branched chain alkanes.
• Figure 3 is a relative area integration for each of the oligomers by carbon number for the GC-MS chromatogram of Figure 2.
• the relative abundance areas are derived from the total ion count for the peaks of that particular set of oligomers (e.g., C 24 ). Yields of 98% or more with some loss of product due to filtration, handling and transfer were obtained. This advantageously also enables the entire procedure to be performed using simple Schlenk techniques while avoiding using a glovebox. At this time, the exact chemical differences/changes in the new active catalyst are not specified; however, the results are very consistent from run to run for this new catalyst preparation.
• the mixture of Ci6-alkene isomers has a measured density of about 0.80 g mL that is similar to pure linear «-hexadecane (0.773 g/mL).
• One of the unique and useful features for these 1- butene derived fuels is the high degree of branching (100%) yet a good overall retention of fuel density.
• a cetane rating for jet fuels is not specified nor directly related to any performance parameter, there is interest to further evaluate these fuels for their respective cetane and octane ratings. Extensive and regular ethyl branching is not typically found in fuel blends; therefore, an appropriate model for predicting a cetane rating is not presently available.
• Fuel density is an important parameter that contributes to meeting fuel performance requirements and may ultimately determine if a biojet version of JP-5/JP-8 can indeed meet or exceed mission critical Department of Defense (DoD) requirements.
• DoD mission critical Department of Defense
• GC/MS Analysis Methods 0.5 mg of oligomer mixture was dissolved in 1.0 mL of methylene chloride. 1 ⁇ L ⁇ of sample was injected into an Agilent 6890 gas chromatography (GC) system equipped with a Restek RTX-5MS 30-meter column. The GC inlet temperature was 250 °C, the initial column temperature was 40 °C held at 3 min, and the temperature was increased at 10° C/min up to a final temperature of 350 °C. An Agilent mass selective detector 5973 system was used to identify the sample components.
• GC gas chromatography
• Butene oligomers 400 g were placed in a 3-neck flask with a gas outlet. The solution was degassed and the atmosphere was replaced with nitrogen. PtO? (400 mg, 1.76 mmol) was added and the mixture was placed under a continuous hydrogen pressure of 2 psig (about 115 kpa).
• PtO? 400 mg, 1.76 mmol
• the reaction could be conveniently monitored by NMR spectroscopy, but flocculation of the catalyst occurred upon completion of the reaction and was subsequently used to determine the end point. After 24 h the reaction mixture was filtered through glass wool to give a quantitative yield of colorless liquid.
• Embodiments of the invention include the conversion of a significant byproduct of 1- butene oligomerization into a hydrocarbon mixture suitable as a stand-alone or component of both turbine and diesel fuel.
• Embodiments include a selective and high yielding (90+%) method for dimerizing 2-ethyl- l-hexene to a complex hydrocarbon mixture, utilizing environmentally favorable solid acid catalysts.
• Embodiments described in related applications detailed a method for producing a JP-5 equivalent fuel from 1-butene.
• 1-butene can be derived from butanol which can be derived from biomass, this permits an efficient process to convert biomass to full performance jet fuels.
• the related process converts 98% of the 1-butene into oligomers, with ca. 40% of the product mixture composed of 2-ethyl-l-hexene.
• the flashpoint of this latter compound is too low to incorporate into JP-5 mixtures (flashpoint: 60°C), although JP-8 mixtures (flashpoint: 38°C) may include up to ca. 15% of this hydrocarbon.
• JP-8 mixtures flashpoint: 38°C
• This renewable fuel can be used as either a stand-alone fuel or can be blended back in with the butene oligomer (JP-5 equivalent) fuel. In either case, the effective dimerization of 2-ethyl-l-hexene permits for a 1-butene to jet fuel conversion of >90%.
• the cation exchange resins Amberlyst-15 and Nafion readily dimerized 2-ethyl-l-hexene at elevated temperatures.
• the degree of hydration strongly affected the rate of isomerization/dimerization.
• saturated dimer mixtures could be isolated in up to 90% yield.
• the dimers have a density of 0.78 g/mL and a freezing point ⁇ -60°C, suggesting that they can be blended with renewable or conventional jet fuels, without adversely affecting the overall density and low temperature viscosity of the mixtures.
• a higher alcohol including biobutanol has several advantages over ethanol. Butanol has a higher flashpoint, is less corrosive, is easier to separate from water, and can be transported in existing pipelines. (Durre, P. Biotech. J. 2007, 2, 1525-1534). Perhaps most importantly, butanol has roughly 135% the volumetric heating value of ethanol, allowing it to be used as a direct replacement for gasoline in automobiles with virtually no change in gas mileage or performance. Biobutanol can be blended with conventional diesel and biodiesel fuels (Chotwichien, A.; Luenguaruemitchai, A.; Jai-h , S.
• butanol has potential as an automobile fuel, it has limited use as a high performance military fuel due to its relatively low flashpoint and the presence of oxygen which limits its net heat of combustion.
• a fully saturated fuel mixture can be obtained through the oligomerization of 1-butene, followed by hydrogenation. (Wright, M. E.; Harvey, B. G.; Quintana, R. L. Energy Fuels 2008, 22, 3299-3302).
• 1-butene can be derived from biobutanol through dehydration, this process allows for the synthesis of high performance jet and diesel fuels from renewable sources.
• the oligomerization is carried out with the use of a Ziegler Natta catalyst system and produces primarily 1 ,2-insertion products (Scheme 9).
• the optimized process for the synthesis of fuel range oligomers (CI 2, CI 6) without concomitant production of heavy oligomers can yield up to 40 mass % dimer.
• To develop an efficient method to incorporate dimer into the overall fuel mixture without adversely affecting the flash point methods to dimerize 2-ethyl-l-hexene, followed by hydrogenation, to produce Ci63 ⁇ 44 molecules were investigated (Scheme 10).
• Liquid superacid catalysts including triflic acid, can also be used for alkylation and addition reactions, yet they can often lead to unproductive cracking reactions (Olah, G. A.; Batamack, P.; Deffieux, D.; Torok, B.; Wang, Q.; Molnar, A.; Prakash, G. K. S. Applied Catalysis A: General 1996, 146, 107-1 17) that may result in lower overall yields of dimers.
• Solid acid catalysts including sulfated zirconia, acid treated clays, and cation exchange resins, may offer the ability to selectively dimerize challenging olefins including 2-ethyl-l-hexene while limiting cracking reactions and offering additional benefits such as easy separation and minimal work-up.
• Nafion 5% water alcohol dispersion
• Montmorillonite K-10 Montmorillonite K-10
• Amberlyst-15 dry Amberlyst-15 were purchased from Aldrich.
• Dowex HCR-W2 hydrated cation exchange resin
• Sulfated zirconia was prepared from ZrOCl 2 -8H 2 0 by a published method.
• Nafion was precipitated from its dispersion by addition of C3 ⁇ 4C1 2 and ether, followed by filtration and drying under vacuum (1 Torr) at ambient temperature.
• MMT K-10 was dried under vacuum (1 Torr) at 140°C for 5 h. Dry Amberlyst-15 and Dowex HCR-W2 were used directly from the bottle. 2-Ethyl-l-hexene was prepared from 1-butene and was distilled from CaH 2 prior to use. Its purity was >99% with trace amounts of 3-methylheptane present. All reactions were performed under a nitrogen environment. All NMR data were collected on a Bruker Avance ⁇ 300 MHz spectrometer.
• the mixture was vigorously stirred and heated to the reflux temperature of 2-ethyl-l- hexene (1 16 °C) in an oil bath.
• the reaction was periodically monitored by NMR to determine the conversion to dimer molecules.
• the reaction was allowed to proceed for 2 h and was then cooled to room temperature.
• the dimer mixture was then separated by decantation to yield a pale yellow solution containing primarily dimer molecules (ca. 90% by GC/MS). After hydrogenation, fractional distillation gave a colorless dimer fraction.
• the solid acids included sulfuric acid treated montmorillonite clay (MMT-K10), a cross-linked polystyrene based hydrated cation exchange resin (Dowex HCR-W2), a macroreticular cation exchange resin (Amberlyst -15), sulfated zirconia, and Nafion (a perfluorinated sulfonic acid resin).
• MMT- 10 which has been utilized for the dimenzation of activated olefins such as 1 ,1-diphenylethene, (Madhavan, D.; Murugalakshmi, M; Lalitha, A.; Pitchumani, K. Catalysis Letters 2001 73, 1-4) and more recently, ⁇ -pinene and its ring opened isomers, (Harvey, B.G.; Wright, M.E.; Quintana, R.L. Preprints of Symposia-ACS Div. Fuel Client. 2009, 54, 305-306) was used without modification in a dimerization reaction. At room temperature, no reaction occurred, while at the reflux temperature (116°C) complete isomerization to a mixture of 4 isomers was observed (Scheme 11).
• activated olefins such as 1 ,1-diphenylethene
• MMT- 10 Suitably dried MMT- 10 was utilized as a catalyst and revealed the ability to slowly isomerize 2-ethyl-l- hexene at room temperature but provided similar results to wet MMT-K10 at reflux temperatures and led to no dimerization products.
• Sulfated zirconia which is an active catalyst for alkylation reactions and is often considered to have acidity comparable to sulfuric acid(Y adav, G. D.; Nair, J. J. Microporous Mat. 1999, 33, 1-48; Valyon, J.; Onyestyak, G.; Lonyi, F.; Barthos, R. J. Phys. Chem.
• MMT-K10 reacts exothermically at room temperature, whereas stronger heterogeneous acids including Nafion are unreactive except under reflux conditions.
• a potential explanation for this behavior is that MMT-K10 (an aluminosilicate clay) has Lewis acid sites that can interact with and bind the incoming olefin. This may aid in bringing the olefin in close proximity to the catalyst surface where the olefin can be protonated by a Bronsted acid site at the clay surface.
• alkenes including 2-ethyl-l-hexene, one can propose a mechanism in which the alkene is coordinated by a Lewis acid center and then is readily isomerized by a nearby acid group.
• the potential interaction of 2-ethyl-l-hexene with MMT-K10 is shown below.
• Nafion a well-studied superacid catalyst that has applications in alkylation and Friedel- Crafts chemistry, olefin isomerization and dimerization reactions
• Molnar A. Curr. Org. Chem. 2008 12, 159-181 Olah, G. A.; Prakash, G. K. S. Molnar, A. Sommer, J. Superacid Chemistry, 2nd Edition, Wiley, 2009; Laufer, MC; Bonrath, W.; Hoelderich, W. F. Cat. Lett. 2005, 100, 101-103; Beltrame, P. Zuretti, G. Applied Cat. A-Gen. 2005, 283, 33-38; Wang, H.; Xu, B. Q.
• H 0 is often used to describe the acidity of solid acid catalysts, a simple comparison of this value across different catalyst types and in different environments with different substrates is ineffective for the prediction of behavior.
• dry Montmorillonite-KlO with H 0 as low as -8.2, efficiently promotes the room temperature isomerization of 2-ethyl-l-hexene, but is completely inactive for the dimerization of the olefin.
• sulfated zirconia which has been characterized as having a Hammet acidity of -12 is also ineffective for dimerization.
• the proposed product structures each include at least two stereocenters, resulting in a total of 18 GC resolvable isomers, not including more complicated alternative mechanisms including cracking, rearrangements, methyl shifts, and cyclization.
• the product distribution is very complex; however, the presence of a variety of isomers in solution is beneficial for a potential fuel mixture as it often prevents crystallization and improves the low temperature fluidity of the fuel.
• Evidence for this effect is provided by the observation that the mixture did not freeze even after being submerged in a -78°C bath for 2 hours.
• the density of the Ci 6 H 34 mixture was 0.78 g/mL.
• Ci 6 H 34 hydrocarbons has been developed. This process allows for the conversion of 1-butene to jet fuel range hydrocarbons in greater than 90% yield.
• Inorganic catalysts such as sulfated zirconia and MMT-K10 efficiently isomerize 2-ethyl-l-hexene, but do not promote dimerization.
• Dry cationic exchange resins including National and Amberlyst-15 produce primarily dimers and small amounts of trimers. The results with native National suggest that National nanocomposites would be ideal catalysts for the dimerization reaction.
• the difference in reactivity between the inorganic catalysts and the cation exchange resins is attributed to interactions between alkenes and Lewis acid centers that inhibit the dimerization reaction. Further work to determine key fuel properties for hydrocarbon mixtures composed exclusively of 2-ethyl-l-hexene dimers as well as mixed systems with hydrogenated butene oligomer mixtures is also being examined.
• Embodiments of the invention clearly have military and commercial applications including oil and biofuel companies which may invest in butanol fermentation, refiners, as well as companies that produce polyolefins for polymer applications.

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