METHOD TO PRODUCE AN ALTERNATIVE SYNTHETICALLY DERIVED AVIATION TURBINE FUEL - SYNTHETIC PARAFFINIC KEROSENE (SPK)

Abstract

The invention provides a process for the production of aviation turbine fuel. The process includes the steps of oligomerizing light olefins derived from a high temperature Fisher-Tropsch process over a zeolite catalyst selected from a ZSM-5 (Zeolyst Int., SiO2/A12O330)(COD-9) at pressures of 50 bar with the temperature ranging from 150 to 310 C., distilling from a gasoline fraction of the oligomerisation product, a fraction boiling below 150 C., hydrogenating the distilled oligomerisation fraction over a hydrogenation catalyst, distilling from the hydrogenated hydrocarbon product, fractionating the hydrogenation distillate fraction over a fractionation catalyst and distilling the fractionation hydrocarbon product to produce an aviation turbine fuel (ASH1925) able to meet the requirements as set out for a Synthetic ISO-Paraffinic Kerosene (SPK) as per ASTM D 7566-14a.

Claims

1. A process for the production of aviation turbine fuel includes the steps of: oligomerizing light olefins derived from a high temperature Fisher-Tropsch process over a zeolite catalyst selected from a ZSM-5 (Zeolyst Int., SiO.sub.2/Al.sub.2O.sub.330)(COD-9) (MFI type catalyst as defined by the International Zeolite Association (IZA) catalyst supplied by Sud Chemie at pressures of 50 bar, the temperature ranging from 150 to 310 C.; distilling gasoline fraction from the oligomerisation product, a fraction boiling below 150 C.; hydrogenating the distilled oligomerisation fraction over a hydrogenation catalyst; distilling from the hydrogenated hydrocarbon product; fractionating the hydrogenation distillate fraction over a fractionation catalyst; and distilling the fractionation hydrocarbon product to produce an aviation turbine fuel (ASH1925) able to meet the requirements as set out for a Synthetic ISO-Paraffinic Kerosene (SPK) as per ASTM D 7566-14a.

2. An aviation turbine fuel process as claimed in claim 1, wherein the ASH1925 aviation turbine fuel is further processed by further hydrogenation to produce a Synthetic Iso-paraffinic (SIP) comprising only iso-paraffins and cyclic paraffins and selecting the feedstock for the production of hydroprocessed synthesized iso-paraffins from plant material, FT-olefins, crude derived olefins and alcohols derived from the fermentation route of sugars or from a FT-process.

3. (canceled)

4. An aviation turbine fuel process as claimed in claim 1, wherein the oligomerization reaction takes place in a multiple fixed bed reactor system charged with a zeolite shape selective catalyst.

5. An aviation turbine fuel process as claimed in claim 2, wherein the SPK fuel produced comprises mostly of iso-paraffins & cyclo-paraffins and mono-aromatic species (single ring alkyl benzenes).

6. An aviation turbine fuel process as claimed in claim 2, the fuel (ASH1925-COD Distillate) is further processed, hydrogenated and fractionated, to produce an alternative Synthetic Iso-paraffinic (SIP) fuel with a near zero sulphur and aromatic content.

7. An aviation turbine fuel process as claimed in claim 2, wherein the SIP is used as a blend material with crude derived kerosene.

8. An aviation turbine fuel process as claimed in claim 1, after hydrogenation, the distillate comprises mostly of the following hydrocarbon types; n-paraffins (<10%), iso-paraffins (50 to 80%), cyclo-paraffins (5 to 30%) and mono-aromatics (3 to 15%).

9. An aviation turbine fuel process as claimed in claim 1, which includes the step of further deep hydrogenation to hydrogenate the mono-type aromatics to their corresponding cyclo-paraffins the fuel comprising of only iso-paraffins and cyclic paraffins.

Description

DESCRIPTION OF THE INVENTION

[0022] This invention describes a process to produce aviation turbine fuel.

[0023] The process for the production of aviation turbine fuel includes the steps of:

[0024] oligomerizing light olefins derived from a high temperature Fisher-Tropsch process over a zeolite catalyst selected from a ZSM-5 (Zeolyst Int., SiO.sub.2/Al.sub.2O.sub.330)(COD-9) (MFI type catalyst as defined by the International Zeolite Association (IZA) catalyst supplied by Sud Chemie at pressures of 50 bar, the temperature ranging from 150 to 310 C.;

[0025] distilling from a gasoline fraction of the oligomerisation product, a fraction boiling below 150 C.;

[0026] hydrogenating the distilled oligomerisation fraction over a hydrogenation catalyst;

[0027] distilling from the hydrogenated hydrocarbon product;

[0028] fractionating the hydrogenation distillate fraction over a fractionation catalyst; and

[0029] distilling the fractionation hydrocarbon product to produce an aviation turbine fuels able to meet the requirements as set out for a Synthetic ISO-Paraffinic Kerosene (SPK) as per ASTM D 7566-14a.

[0030] The above method may include a further hydrogenation step to produce Synthetic Iso-paraffinic (SIP) fuel with a near zero sulphur and aromatic content.

[0031] The process converts light olefins (C.sup.=3, C.sup.=4, C.sup.=5, C.sup.=6 or higher) derived from the Fischer Tropsch (FT) process to produce a longer chain distillate. The reaction takes place in a multiple fixed bed reactor system charged with a zeolite shape selective catalyst, COD-9. Multiple reactions take place almost simultaneously, the main reaction being oligomerization followed by cracking and isomerization.

[0032] An important aspect is the reaction conditions where the olefins contact with the catalyst at pressures of 50 bar, the temperature profile ranges from 150 to 310 C.

[0033] The COD reactor product comprises of a wide range of carbon 5 plus hydrocarbon products that are fractionated into gasoline and distillate, the fraction typically boiling below 150 C. reports to the gasoline pool. Once the distillate fraction is hydrogenated and further fractionated to meet the desired specification the product can then be termed as ASH 1925 or Synthetic Iso-Paraffinic Kerosene (SPK).

[0034] This SPK produced by this production route possess unique properties making it highly desirable for use as aviation turbine fuel or blend component. These bulk fuel properties include near zero Sulphur content, high energy density combined with excellent cold flow and combustion properties.

[0035] The SPK fuel produced by this route comprises mostly of iso-paraffins & cyclo-paraffins and mono-aromatic species (single ring alkyl benzenes). Thus the second aspect of this invention are the fuels exceptional cold flow properties, due to its molecular composition making it an ideal aviation turbine fuel that is fully fungible within the fuel transport systems.

[0036] The oligomerisation process acts an enabler for stand-alone refineries, in particular, synthetic fuel refineries, enabling them to convert light olefinic feedstock to distillate. Once hydrogenated and fractionated, aviation turbine fuel having favourable emission characteristics and exceptional cold flow properties is produced. The above mentioned fuel readily meets the requirements of the Standard Specification for Aviation Turbine Fuels Containing Synthesised Hydrocarbons (ASTM D7566) for Jet A and Jet A1 as well as the extended properties as defined in part 2.

[0037] The latter fuel (ASH1925 -COD Distillate) can be further processed to produce a novel alternative Synthetic Iso-paraffinic (SIP) fuel with a near zero sulphur and aromatic content. This SIP is a perfect blend material with crude derived kerosene enabling it to meet stringent aviation turbine fuel specifications that the unblended crude fuel alone could not achieve. The feedstock from the COD process once hydrogenated and fractionated is further hydrogenated to produce a SIP. This fuels meets the specifications as per ASTM D7566-14a, Table A3.1. The only exception being that the feedstock for the production of hydroprocessed synthesized iso-paraffins does not only come from plant material, it may come from FT-olefins, crude derived olefins and alcohols derived from the fermentation route of sugars or from the FT-process.

[0038] FIG. 2 provides a brief process description of the COD process fit into a GTLR including alternative feed options

[0039] As the COD distillate exits the reactor it is fractionated into the Gasoline and Distillate via a Gasoline-Distillate (GD) splitter column. The distillate boiling range can vary but typically ranges from 150 to 360 C. The raw distillate that is at this point highly olefinnic and has a Bromine Number of above 80 g Br/100 g sample.

COD Distillate Upgrading

[0040] Distillate produced by the COD process is hydrotreated to convert the olefins to their corresponding paraffins. At this point the distillate comprises mostly of the following hydrocarbon types; n-paraffins (<10%), iso-paraffins (50 to 80%), cyclo-paraffins (5 to 30%) and mono-aromatics (3 to 15%). The distillate is highly branched. The high degree of branching was confirmed by GCGC-MS and NMR studies. Further modelling studies show that the branching is mostly methyl groups and 1 methyl group for every 3 carbons is envisaged.

[0041] Once the product exits the hydrotreater it is fractionated into the desired fractions. At this point the product meets the detailed requirements as per ASTM D7566 for Aviation Turbine Fuels Containing Synthesised Hydrocarbons as a Synthetic Paraffinic Kerosene (SPK), lubricity being the only exception.

[0042] In a third step, further upgrading could be done to convert the mono-type aromatics to their corresponding cyclo-paraffins, where after the resultant product would meet the Synthetic Iso-paraffin (SIP) specification. The product would then comprise of only iso-paraffins and cyclic paraffins.

[0043] Table 1 highlights the hydrocarbon type composition as produced for both synthesis routes. Hydrocarbon type determination was performed by 1212 Matrix Mass Spectrometry for both the SPK and SIP as produced.

TABLE-US-00001 TABLE 1 Sample SPK SIP Prep HPLC Analysis Saturates 89.6 100 Aromatics 10.4 0 Polars 0 0 12 12 MS Matrix Method Paraffins CnH2n+2 66.9 84 Mono cyclo paraffins CnH2n 18.8 15.9 Di cyclo paraffins CnH2n2 2.8 0 Tri clyclo paraffins CnH2n4 0 0 Tetra cyclo paraffins CnH2n6 0 0 Total saturates 88.5 100 Alkyl Benzenes CnH2n6 8.3 0 Benzo cylo paraffins CnH2n8 3.2 0 Benzo dicyclo paraffins CnH2n10 0 0 Naphthalenes CnH2n12 0 0 Acenapthenes/Biphenyls CnH2n14 0 0 Total Aromatics 11.5 0

[0044] While the 1212 MS results give detail of the hydrocarbon nature of the fuel the degree of branching is not illustrated by this analytical technique.

[0045] The distillates degree of alkane branching was determined by NMR whereby a branching index of 0.8 was derived, indicating that the distillate product as synthesised is highly branched. The degree of branching, type of hydrocarbons, especially aromatics heavily impact the H/C ratio on a molecular level that directly impacts the fuel properties.

[0046] Once upgraded by hydrogenation and fractionation to a 150 to 250 C. the resultant fuel is sulphur free and has superior cold flow properties (CFPP <45 C.) and has a relatively low aromaticity content.

EXAMPLE 1 (ASH 1925-JP8 and SPK)

[0047] It is an object of this invention to provide synthetically derived aviation turbine fuel capable of meeting the ASTM D7566-14a, using the existing refinery configuration at the PetroSA, Mossel Bay GTLR. The resultant fuel should have excellent cold flow properties over a relatively wide boiling range, have excellent burn characteristics and not impact the flash point.

[0048] The PETROSA COD process involved contacting the olefinnic feed comprising of the following olefins; C.sup.=3, C.sup.=4, C.sup.=5, C.sup.=6 with a zeolite type catalyst (selected from the group consisting of a COD-9 catalyst and a ZSM-5 catalyst). The reactor pressure was 45 bar gauge, and a reactor feed temperature maintained such that the delta across the 3-reactors did not exceed 30 C., the temperature profile for all 3-fixed bed reactors ranged from 200 to 310 C. to produce a COD distillate.

[0049] The olefinic distillate taken from the G/D splitter was hydrogenated in a Distillate Hydrotreater (DHT) charged with a commercial cobalt molybdenum catalyst. The reaction temperature was at 280 C. at pressure was maintained 5000 to 8000 kPa. The hydrogen to hydrocarbon ratio was maintained at about 400 nm.sup.3/hr at LHSV of between 0.3 and 1. Once hydrotreated the distillate was fractionated to yield a light naphtha fraction, a kerosene mid-boiling range distillate (boiling range) and a diesel fraction boiling above 250 C.

[0050] The mid boiling range kerosene (190 to 250 C.) was further evaluated for its suitability as an aviation turbine fuel. The fuel was marked as an FT fuel and submitted to a credible independent fuels testing laboratory, DOD Jet Propulsion Laboratory under the testing code of #5290. In-house PetroSA termed the same fuel ASH1950.

TABLE-US-00002 TABLE 2 Results of the fuel specification testing FT - 5290 4751 JP-8 Specification Test Total Acid Number, mg KOH/g 0.002 0.003 Aromatics, vol % 5.2 18.8 Olefins, vol % 1.2 0.8 Mercaptan Sulfur, % mass 0 0 Total Sulphur, % mass 0 0.04 Distillation: IBP, C. 192 159 10% recovered, C. 200 182 20% recovered, C. 203 189 50% recovered, C. 212 208 90% recovered, C. 240 244 EP, C. 264 265 Residue, % vol 1.2 1.3 Loss, % vol 0.6 0.8 Flash point, C. 71 51 Cetane Index (calculated) 64.9 46 Freeze Point, C. <78 50 Viscosity @ 20 C., cSt 6.5 4.9 Viscosity @ 40 C., cSt 15.1 9.9 Heat of Combustion (measured), BTU/lb 18900 18600 Hydrogen Content, % mass 14.8 13.8 Smoke Point, mm 40 22 Copper Strip Corrosion 1a 1a Thermal Stability @ 260 C.: Tube Deposit Rating 1 1 Change in Pressure, mm Hg 0 2 Existent Gum, mg/100 mL <1 0.4 API Gravity @ 60 F. 49.8 44.4 Specific Gravity @ 15 C. 0.78 0.804 Lubricity (BOCLE), wear scar mm 0.76 0.53

[0051] It should be noted that this particular batch fuel was limited in terms of aromatic content, less than 8% v/v but still performed well over the tests. The aromatic content is further discussed later in this specification.

[0052] A comparison of the FT 5290 (ASH 1925) sample compared to JP-8 is given in Table 3.

TABLE-US-00003 TABLE 3 Comparison of F-T 5290 or COD (ASH1925) sample compared to JP-8. F-T Properties 5290 JP-8 Average JP-8 Spec Paraffins (normal + iso), vol % 90 ~60 (+~20% cyclo paraffin) Aromatics, vol % (D1319) 0 17.9 25 Specific gravity (D4052) 0.78 0.803 0.775-0.840 Flash point, C. (D93) 71 49 38 Freeze point, C. (D5972) <78 51.5 47 Hydrogen content (D3343), 14.8 13.8 13.4 mass % Heat of combustion, MJ/kg 43.9 43.2 42.8 (D4809) Smoke point, mm 40 23 19

[0053] Tables 2 and 3 indicate that the ASH 1925 fuel has a superior hydrogen content and heat of combustion as compared to JP-8 used as a reference fuel. The density is lower than the average JP-8 fuel but still within the density specification.

[0054] Aromatics as per ASTM D1319 were non-detectable on sample F-T 5290 fuel. While the a aromatic content may seem to be of some concern since a of 8% v/v aromatics is desired, aromatic synthesis in the COD process is quite controllable and it is possible produce a total mono-aromatic content of above 8% v/v by running the COD reactor inlet temperature higher. Table 4 offers the aromatic speciation as performed by the external US Testing Laboratory.

TABLE-US-00004 TABLE 4 Aromatic speciation of FT- 5290 (ASH 1925) compared to JP-8. FT-5290 4751 - JP-8 F-T JP-8 D 6379 (vol. %) FP: <78 C. FP: 51 C. Mono-aromatics 3.7 18.2 Di-aromatics <0.2 1.4 Total Aromatics 3.7 19.6 Total Saturates 96.3 80.4

[0055] FIG. 3 provides the GC traces of the FT 5290 compared to JP-8

[0056] As can be seen in Table 3 that there is no fuel like FT-5290 since it contains almost no n-paraffins (less than 1 weight %) however all the iso-paraffins fall in the desired boiling range of C10 to C16 as with JP-8.

[0057] FIG. 4 shows a Scanning Brookfield viscometer trace of the FT 5290 fuel compared to JP-8 and other FT fuels.

[0058] (ASH 1925) has better viscosity properties than traditional JP-8 where with the JP-8 fuel the viscosity drops away at a temperature of near 55 C., its freeze point temperature. While the PetroSA ASH 1925 viscosity at 40 C. is 15.1 cP, higher than the JP-8, the ASH 1925 (FT 5290) remained in the liquid until state beyond 70 C.

[0059] As can be seen in latter example, the fuel tested at the US Jet Propulsion Laboratory compared well with the JP-8 fuel, the exception being that of aromatic content. The fuel clearly was more resilient in terms of cold flow properties, with a freeze point of <78 C., a high hydrogen content of 14.8% mass, good oxidation stability and a superior calorific value. From the latter it is clear that the ASH 1925 (FT 5290), is well suited as a reliable alternative aviation turbine fuel used neat or as a blend component.

EXAMPLE 2 (COD Kerosene-SPK)

[0060] Light olefins in the carbon range C3 to C6 originating from a High Temperature Fischer Tropsch (HTFT) plant located in Mossel Bay were oligomerised over a proprietary zeolyte catalyst (COD 9). The oligomerisation reaction was performed at moderate temperatures below 300 C. and at relatively high pressures of 45-bar process for the oligomerisation reaction to produce an olefinic distillate with a Bromine Number of over 90 g Br/100 g sample. The olefinic portion of the sample was hydrotreated at moderate hydrotreating conditions in Diesel Hydrotreater unit (Unit 35) equipped with a cobalt molybdenum catalyst, at 58 kPa, the WABT did not exceed 321 C., the LHSV was maintained at 0.6 while the Hydrogen to Hydrocarbon Ratio was 275. A hydrotreated fraction boiling between about 190 to 250 C. was collected.

[0061] SPK samples from the GTLR test run were tested for verification of the hydrocarbon types. HPLC, 1212 MS and GC-FI MS characterisation techniques were used. The results thereof are given in Table 5.

[0062] It was clear that the plant could be run in a higher aromatic mode and that the aromatic type was still mono-aromatic species. The aromatic species being mono-aromatics was important since these species have a better H/C ratio than any other aromatic. Further it was important to confirm the absence multiple ring aromatics that do not have a favourable impact on H/C ratio, and are deemed as carcinogens.

[0063] A lower H/C ratio results in higher calorific values for the fuel, have better combustion properties and have a lower smoke point. A production sample was tested for hydrocarbon type composition and aromatic content by GC-FI MS, the presence of single ring aromatics was confirmed. This is illustrated in Table 5.

TABLE-US-00005 TABLE 5 GC-FI MS of ASH 1925 ASH 1925 Z Number +2 0 2 4 6 8 10 Carbon CnH2n + 2 CnH2n CnH2n 2 CnH2n 4 CnH2n 6 CnH2n 8 CnH2n 10 Number Alkanes 1-CycloA 2-CycloA 3-CycloA Alk-Benz BenCycl BendiCyc 10 2.74 0.86 0.09 0.10 1.32 0.02 0.00 11 10.26 2.18 0.16 0.00 1.34 0.06 0.00 12 16.46 3.35 0.42 0.03 1.91 0.30 0.00 13 14.93 3.46 0.82 0.00 1.80 0.27 0.03 14 11.75 3.07 0.62 0.04 1.21 0.28 0.07 15 6.89 2.58 0.46 0.03 0.64 0.19 0.00 16 3.23 1.36 0.32 0.04 0.35 0.16 0.00 17 1.53 0.70 0.13 0.00 0.16 0.06 0.00 18 0.34 0.25 0.08 0.00 0.04 0.00 0.00 19 0.12 0.13 0.03 0.00 0.00 0.02 0.00 20 0.03 0.00 0.00 0.00 0.00 0.00 0.00 21 0.03 0.00 0.00 0.00 0.00 0.00 0.00 22 0.02 0.00 0.00 0.00 0.00 0.00 0.00 Totals 68.32 17.97 3.15 0.24 8.77 1.35 0.14

[0064] Having confirmed the presence of aromatics in some detail it was decided to confirm the level of isomerisation of the paraffin species, multidimensional GCGC-TOF MS was selected as analysis technique. A high ratio of normal-paraffins to iso-paraffins was confirmed and illustrated as can be seen in Table 6. The ratio of normal to iso-alkanes was 0.49 to 70.64. This high degree of branching contributes to the fuels unique hydrocarbon type composition.

TABLE-US-00006 TABLE 6 GC GC TOF MS of ASH 1925 ASH 1925 Carbon Number n-Alk Iso-Alk cyclic-Alk Di-Cyclic-Alk Tri-Cyclic-Alk Aromatics Naphth 9 0.00 0.02 0.03 0.00 0.00 0.10 0.00 10 0.04 0.42 0.41 0.01 0.00 0.66 0.00 11 0.26 1.91 1.35 0.08 0.00 1.50 0.00 12 0.09 5.34 3.46 0.23 0.01 2.05 0.00 13 0.06 9.47 5.87 0.33 0.00 1.98 0.00 14 0.01 13.79 3.12 0.06 0.01 1.38 0.00 15 0.01 31.20 1.89 0.02 0.00 0.78 0.00 16 0.00 5.81 1.17 0.32 0.00 0.41 0.00 17 0.00 1.84 0.51 0.04 0.00 0.12 0.00 18 0.00 0.67 0.11 0.02 0.00 0.02 0.00 19 0.00 0.17 0.03 0.00 0.00 0.00 0.00 20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 21 0.00 0.00 0.00 0.00 0.00 0.00 0.00 22 0.02 0.00 0.00 0.00 0.00 0.00 0.00 Totals 0.49 70.64 17.95 1.11 0.02 9.00 0.00

[0065] The hydrocarbon type analyses having been validated on a molecular level the physical properties of the fuel against the ASTM specification were tested. Table 7 compares the ASTM detailed requirement for Synthesized Hydrocarbons (SPK) for use in aviation turbine fuels Part 1, these requirements are readily met.

[0066] Tests performed on various samples produced from this process for trace metals by test method ASTM D3605, for Sodium, Potassium, Lead, Calcium, Lithium and Vanadium, were below the methods detection limit.

TABLE-US-00007 TABLE 7 ASTM 7566 - Part 1 Specification versus ASH1925 (SPK) Detailed Requirements of Aviation Turbine Fuels Containing Synthesized Hyrocarbons Part 1 - Basic Requirements SPK Jet A or (ASH Property Unit Jet A1 Test Method 1925) COMPOSITION Appearance C & B C & B Acidity, Total mg KOH/g Max. 0.015 D3242 IP 354 0.002 Aromatics vol % Max. 25.0 D1319/IP 156 (IP 391) 9 or Total Aromatics vol % Max. 26.5 D6379/IP 436 Sulphur, Total wt % Max. 0.30 D1266, D1552, D5453 <0.001 Sulphur, Mercaptan wt % Max 0.0030 D3227/IP342 <0.001 or Doctor Test Negative D4952 Neg VOLATILITY Distillation Temperature: Initial BP C. Report D86, D2887/IP 406 191 10% Recovery C. Max. 205 196 50% Recovery C. Report 207 90% Recovery C. Report 241 Final BP C. Max. 300 250 Distillation Residue vol % Max. 1.5 1.1 Distillation Loss vol % Max. 1.5 0.5 Flash Point C. Min. 38 D56 or D 3828, IP170 71 Density @ 15 C. kg/m3 775-840 D1298/IP 160 or D4052 Density @ 20 C. kg/m3 771.3-836.6 D1298/IP 160 or D4052 0.7787 FLUIDITY Freezing Point C. Max. 40 (Jet A) D2386/IP 16, D5972/IP435 <78 Viscosity @ 20 C. cSt or (mm.sup.2/s) Max. 8.0 D445/IP 71 6.5 COMBUSTION Net Heat of Comb. MJ/kg Min. 42.8 D4529, D3338, D4529 46.7 Smoke Point mm Min. 25 D1322/IP 57 44 or Smoke Point mm Min. 19 D1322/IP 57 and Naphthalenes vol % Max. 3.0 D1840 CORROSION Copper Strip 2 h @ 100 C. Max. 1 D130/IP 154 1a THERMAL STABILITY JFTOT P @ 260 C. mm Hg Max. 25.0 D3241/IP 154 0 Tube Deposit Rating Visual Max. <3 1 CONTAMINANTS Existent Gum mg/100 m Max. 7 D381, IP 540 <1 MSEP Rating 7 D3948 Fuel without Condt. Add Min. 85 Not Tested Fuel with Condt. Add. Min. 70 Not Tested OTHER Conductivity pS/m 50-450 D2624/IP 274 Lubricity (BOCLE) diameter, mm Max. 0.85 D5001 0.76 ADDITIVE Electrical conductivity mg/L 17.0-24.0

TABLE-US-00008 TABLE 8 ASTM 7566 - Part 2 Extended Requirements versus ASH1925 (SPK) Part 2 - Extended Requirements SPK Jet A or (ASH Property Unit Jet A1 Test Method 1925) COMPOSITION Aromatics (either) vol % Min. 8 D1319/IP 156 (IP 391) or Total Aromatics vol % Min. 8.4 D6379/IP 436 9 VOLATILITY Distillation D2887/IP 406, D2887 T50 T10 C. Min. 15 T90 T10 C. Min 40 LUBRICITY Lubricity mm Max. 0.85 D5001 0.76 FLUIDITY Viscosity @ 40 C. cSt or Max. 12 D445/IP 71 15.1 (mm.sup.2/s)

[0067] Table 8 indicates the extended Requirement as given in ASTM 7566-14a where a minimum aromatic content of 8 vol % is required is met. The only exception to meeting all the stringent requirements has been the requirement to have a viscosity of lower than 15.1 cSt at 40 C. It should be noted that from FIG. 3, the Scanning Brookfield viscometer trace, the FT 5290 fuel compared to JP-8 and other FT fuels showed that the SPK fuel provided remains in the liquid form without freezing to beyond 78 C.

[0068] The physical properties in Table 7 further illustrate that the requirements of MIL-DTL-83133F (JP-8) Synthetic Paraffinic Kerosene (SPK) to be used either neat or in blends up to 50% v/v can be achieved. A flash point of 71 C. for the SPK where the desired military specification is 68 C. minimum, this is not seen as a problem since a small reduction in the distillation cut point will reduce the IBP, Flash Point and viscosity at 40 C.

EXAMPLE 3

[0069] Light olefins in the carbon range C3 to C6 originating from the High Temperature Fischer Tropsch plant located in Mossel Bay were oligomerised over a proprietary zeolyte catalyst (COD 9). The oligomerisation reaction took place at moderate temperatures below 280 C. and relatively high pressures of 55 bar process were used for the oligomerisation reaction to produce an olefinic distillate with a Bromine Number of over 120 g Br/100 g sample.

[0070] This distillate was further hydrotreated in one step using a supported Platinum commercial catalyst (Axens LD402). The catalyst (270 cc) was charged into a pilot plant a graded bed format and diluted with inert ceramics. The reactor pressure was maintained at 60 bar, the WABT did not exceed 230 C., the LHSV was maintained at 0.9 and a portion of the product was recycled.

[0071] The one step hydrotreated distillate was fractioned by means of a true boiling point distillation apparatus to yield a kerosene fraction in the boiling range 170 C. to 250 C. This kerosene was found to contain less than 0.1% v/v aromatics.

[0072] The above process delivered a ready to go Synthetic Iso-paraffin (SIP) Jet A1 kerosene, the properties thereof are given in Table 9.

TABLE-US-00009 TABLE 9 Physical properties of Mosspar 1925 (Synthetic Iso-Paraffin) Properties Units Test Method Result Density @ 20 C. Kg/L ASTM D 4052 0.7705 Flash Point (PMcc) C. ASTM D 93 66.5 Total Sulphur ppm ASTM D5453 <0.3 (m/m) Colour (Saybolt) ASTM D156 30 Aromatic content % m/m UOP 495 <0.01 Kinematic viscosity @ cSt ASTM D 445 1.878 25 C. Brookfield Viscosity @ cP 2.960 0 C. Heat of Combustion kJ g.sup.1 46.67 (0.1457) Distillation: ASTM D86 IBP C. 189.7 10% v/v C. 20% v/v C. 50% v/v C. 90% v/v C. 232.7 FBP C. 249.2 Distillation Residue ml 0.8

[0073] The biodegradability of the resultant fuel Mosspar 1925 (SIP) was tested in a closed bottle test, on day 21, 91.6% of the product had degraded indicating that this product is readily biodegradable.

[0074] Further to the above testing it was found that the SIP, Mosspar 1925, displayed a low toxicity towards Mysid Shrimp (Mysidopsis bahia) in a 96-Hour toxicity test as per OCSPP 850.1035, the no observed effect concentration was greater than 2000 mg/L. Further testing on 48-Hour acute toxicity testing on Daphnia magna as per OECD 202 and Fathead Minnow (Pimephales promelas) (OECD 203) indicated that the NOEC was 100 mg/l for these organisms indicating limited toxicity.

[0075] The ratio of iso-paraffins to normal paraffins for the SIP fuel is extremely high (nP:iP::2:88), this is characteristic of this process and resultant streams.

[0076] As previously mentioned a high H/C ratio is favoured for aviation fuels since the specific energy would resultantly be higher. Lower H/C ratios result in higher flame radiation that in turn increase carbon deposits and particulate matter (smoke). Typical crude derived fuels have an H/C ratio of about 2. The main driver for low H/C ratios are aromatics especially multiple rings, it is interesting to note that while the COD derived diesel contain aromatics these are all mono or single ring aromatics. Mono-aromatics (alkyl- benzenes) have lower H/C ratio than other aromatic species, 1.5 to 1.8.

[0077] According to the Jet Fuel specification, MIL-DTL-83133F, JP-8 should have a boiling range of between 157 and 300 C. and a density at 15 C. ranging from 0.775 to 0.840 kg/l making both the proposed SPK (ASH1925) and the SIP (Mosspar 1925) fuels as produced in the GTLR (Mossel Bay) highly desirable as aviation turbine fuels.

[0078] In terms of cold flow properties the SPK has a Freeze Point of <78 C. while the SIP and SPK have Cloud Point of well below 40 C. indicating that they are safe to use at high altitudes without any fear of in-line freezing. In the prior art, increased cooling of crude derived fuels after the 1.sup.st crystallisation point (Cloud Point) typically result in a sharp rise in viscosity, with wax crystals evolving and limiting fuel flow. The presence of wax crystals can deposit on the fuel delivery system inner walls blocking in-line filters and injector nozzles leading to catastrophic failure. A Freeze Point of 47 C. is thus important for long haul flights.

[0079] The fuels derived from the COD process, ASH1925 and Mosspar 1925 tend to be low polar boundary solvents content (no heteroatoms) so have limited lubricity, these fuels are however compatible with the approved lubricity and electrical conductivity additives.

[0080] Disclosed are two processes to manufacture safe and reliable alternative fuels with superior combustion qualities. The proposed fuels in the new art are compatible with conventional fuels and would not require additional storage and logistics facilities. Both the SPK and SIP have high Specific Energy, of 46.6 and 46.7 MJ/kg. Converting the Specific Energy to Energy Density the value is in excess of 35 MJ/L not only making them comparable Jet A/Jet A1 but improve on the prior art energy density.

[0081] Due to the fact that they are by nature low in aromatic content they do not tend to form smoke or carbon deposits.

[0082] The proposed fuels are low in existent and potential gums, the presence of gum was tested by ASTM D381 and found to be well within specification. The fuels have low portions of olefins in them that are responsible for gum and polymer formation, olefins are reactive in fuel and as such recommendations are to have not more than 5% olefins in aviation turbine fuels. The SPK and SIP show good resistance to oxidation, oxidised fuels containing gum will tend to deposit as lacquer films (varnish) on the turbine blades that can distort fuel spray patterns and even shear off resulting in turbine damage. While the Bromine Number of the SPK (ASH1925) is below 10 g Br/100 g sample GC-MS characterisation indicates the absence of olefins, both fuels are hydrogenated. In terms of thermal stability the fuels are stable over long periods of time.

[0083] The proposed fuels are virtually free of both sulphur and nitrogen compounds thereby reducing undesirable emissions. Studies performed on vehicles using fuels derived from the COD process have proven over a wide range of test conditions that they are able to simultaneously reduce both particulate matter (smoke) and nitrous oxide emissions.

[0084] The COD fuels ASH1925 and Mosspar1925 are free of poly-aromatic hydrocarbons that contribute to particulate matter and deemed carcinogenic. Fuels with high aromatic contents cause fuel delivery system elastomers to swell, however exposing the fuel to a fuel with lower aromatic content could lead to a reduction in elastomer swell and result in leakages. It is for this reason that the Mosspar1925 fuel that contains <0.01% m/m aromatics to be used a blend stock to upgrade fuels with less desirable properties.

[0085] The ASH1925 fuel contains sufficient aromatics, >8% m/m mono-aromatics to meet the Jet A/Jet A1 and JP-8 aromatic specifications. Of interest the mono-aromatic species while assisting to improve density and combat reductions in seal swell after expose to high aromatic containing fuels the mono-aromatic compounds offer the best in class hydrogen to carbon ratio.

[0086] Provided is a homologous series of iso-paraffinic and cyclic hydrocarbons across the carbon range in the carbon range C10 to C20, the ratio of iso to normal paraffins being at least 10:1 but most likely 40:1.

[0087] The invention provides a process to produce synthetically derived aviation turbine fuels by catalytic conversion of light Fischer Tropsch olefins to distillates (COD) and refining thereof. The production of synthesized iso-paraffins (SIP) and synthesised paraffinic kerosene (SPK) that can be both be used as aviation turbine fuels as a blend component or a fungible drop in component.

[0088] Provided is a process to produce a synthesized iso-paraffins (SIP) (M1925) comprising essentially of iso-paraffins and cyclo-paraffins that can be used as a semi-synthetic aviation turbine fuel blend component in a 50:50 blend ratio.

[0089] In addition to providing a process for the provision of SIP's also provided is a process for producing synthesised paraffinic kerosene (SPK) (ASH1925) that meets the requirements of ASTM D7566 as a fungible turbine fuel.

[0090] The process entails both oligomerisation and isomerisation of Fischer Tropsch derived, or other light olefins, to form hydrocarbons in the distillate boiling range. The reaction takes place over a shape selective zeolyte type catalyst at temperatures of 150 to 320 C. and reactor pressures of 5,5 MPa. Distillate can then be refined by hydrogenation to yield ASTM D7566 compliant SPK. Further processing of resulting the SPK to hydrogenate aromatics to their corresponding cyclo-paraffins yields a SIP.