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The Fischer–Tropsch process (or Fischer–Tropsch Synthesis) is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic lubrication oil or as synthetic fuel.[1] The F-T process has received intermittent attention for a variety of reasons, i.e. as a source of low-sulfur diesel fuel or to address the supply or cost of petroleum-derived hydrocarbons.

Contents

Process chemistry

The Fischer–Tropsch process involves a variety of chemical reactions, which lead to a series of both desirable and undesirable byproducts. Useful reactions give alkanes:

(2n+1) H2 + n CO → CnH(2n+2) + n H2O

where 'n' is a positive integer. The formation of methane (n = 1) is generally unwanted. Most of the alkanes produced tend to be straight-chain alkanes, although some branched alkanes are also formed. In addition to alkane formation, competing reactions result in the formation of alkenes, as well as alcohols and other oxygenated hydrocarbons. Usually, only relatively small quantities of these non-alkane products are formed, although catalysts favoring some of these products have been developed.

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Other reactions relevant to FT

Several reactions are required to obtain the gaseous reactants required for F-T catalysis. All feedstocks entering a FT reactor must be desulfurized, for example. The water gas shift reaction gives the gases that are fed into the reactors:

H2O + CO → H2 + CO2

This reaction is also used to adjust the H2:CO ratio of the gas that is fed to the reactor.

For F-T plants that start with methane, another important reaction is steam reforming, which converts the methane into CO and H2:

2 H2O + CH4 → CO + 3 H2

Chemical mechanisms

The conversion of CO to alkanes involves net hydrogenation and hydrogenolysis of the CO. Such reactions are assumed to proceed via initial formation of surface-bound metal carbonyls. Subsequently, the CO ligand undergoes dissociation to give oxide and carbide centers.[2]. Other potential intermediates in the reduction of CO feature C-1 fragments including formyl (CHO), hydroxycarbene (CH(OH), hydroxymethyl (CH2OH), methyl (CH3), methylidene (CH2), methylidyne (CH), and hydroxymethylidyne (COH). Furthermore, and critical to the production of liquid fuels, are reactions that form C-C bonds, such as migratory insertion. Many related stoichiometric reactions have been simulated on discrete metal clusters, but homogeneous FT catalysts are poorly developed.

Process conditions

Generally, the Fischer–Tropsch process is operated in the temperature range of 150–300 °C (302–572 °F). Higher temperatures lead to faster reactions and higher conversion rates but also tend to favor methane production. As a result the temperature is usually maintained at the low to middle part of the range. Increasing the pressure leads to higher conversion rates and also favors formation of long-chained alkanes both of which are desirable. Typical pressures range from one to several tens of atmospheres. Even higher pressures would be favorable, but the benefits may not justify the additional costs of high-pressure equipment.

A variety of synthesis gas compositions can be used. For cobalt-based catalysts the optimal H2:CO ratio is around 1.8-2.1. Iron-based catalysts promote the water-gas-shift reaction and thus can tolerate significantly lower ratios. This reactivity can be important for synthesis gas derived from coal or biomass, which tend to have relatively low H2:CO ratios (<1).

Product distribution

In general the product distribution of hydrocarbons formed during the Fischer–Tropsch process follows an Anderson-Schulz-Flory distribution,[3] which can be expressed as:

Wn/n = (1-α)2αn-1

Where Wn is the weight fraction of hydrocarbon molecules containing n carbon atoms. α is the chain growth probability or the probability that a molecule will continue reacting to form a longer chain. In general, α is largely determined by the catalyst and the specific process conditions.

Examination of the above equation reveals that methane will always be the largest single product; however by increasing α close to one, the total amount of methane formed can be minimized compared to the sum of all of the various long-chained products. Increasing α increases the formation of long-chained hydrocarbons. The very long-chained hydrocarbons are waxes, which are solid at room temperature. Therefore, for production of liquid transportation fuels it may be necessary to crack some of the Fischer-Tropsch products. In order to avoid this, some researchers have proposed using zeolites or other catalyst substrates with fixed sized pores that can restrict the formation of hydrocarbons longer than some characteristic size (usually n<10). This way they can drive the reaction so as to minimize methane formation without producing lots of long-chained hydrocarbons. Such efforts have met with only limited success.

Fischer-Tropsch catalysts

A variety of catalysts can be used for the Fischer–Tropsch process, but the most common are the transition metals cobalt, iron, and ruthenium. Nickel can also be used, but tends to favor methane formation ("methanation").

Cobalt seems to be the most active catalyst, although iron may be more suitable for low-hydrogen-content synthesis gases such as those derived from coal due to its promotion of the water-gas-shift reaction. In addition to the active metal the catalysts typically contain a number of "promoters," including potassium and copper. Catalysts are supported on high-surface-area binders/supports such as silica, alumina, or zeolites.[4] Cobalt catalysts are more active for Fischer-Tropsch synthesis when the feedstock is natural gas. Natural gas has a high hydrogen to carbon ratio, so the water-gas-shift is not needed for cobalt catalysts. Iron catalysts are preferred for lower quality feedstocks such as coal or biomass.

Unlike the other metals used for this process (Co, Ni, Ru) which remain in the metallic state during synthesis, iron catalysts tend to form a number of chemical phases, including various oxides and carbides during the reaction. Control of these phase transformations can be important in maintaining catalytic activity and preventing breakdown of the catalyst particles.

Fischer-Tropsch catalysts are notoriously sensitive to poisoning by sulfur-containing compounds. The sensitivity of the catalyst to sulfur is greater for cobalt-based catalysts than for their iron counterparts.

LTFT and HTFT

The low temperature F-T process rely on cobalt-based catalysts. Illustrative operations are the original German plants and the Shell Middle Distillate process in Malaysia. LTFT produces blending stock for fuels, not fuels themselves. In contrast, high temperature F-T catalysis, which operates at 300-345 °C and relies on iron-based catalysts, produces fuel grade diesel directly.[5]

Gasification

F-T plants associated with coal or related solid feedstocks (sources of carbon) must first convert the solid fuel into gaseous reactants, i.e. CO, H2, and alkanes. This conversion is called gasification. Synthesis gas obtained from coal gasification tends to have a CO/H2 ratio of ~0.7 compared to the ideal ratio of ~2. This ratio is adjusted via the water-gas shift reaction. Gasification is a dirty and expensive (endergonic) process. Coal-based Fischer–Tropsch plants can produce significant amounts of CO2, in part due to the high energy demands of the gasification process.

Combining [biomass gasification]] (BG) and Fischer-Tropsch (FT) synthesis is a possible route to produce renewable transportation fuels (biofuels).[6]

History

Since the invention of the original process by Franz Fischer and Hans Tropsch, working at the Kaiser Wilhelm Institute in the 1920s, many refinements and adjustments have been made. The term "Fischer-Tropsch" now applies to a wide variety of similar processes (Fischer-Tropsch synthesis or Fischer-Tropsch chemistry). Fischer and Tropsch filed a number of patents, e.g., US patent no. 1,746,464, applied 1926, published 1930.[7] It was commercialized in Germany in 1936. Being petroleum-poor but coal-rich, in Germany the FT-process was used by Nazi Germany and Japan during World War II to produce ersatz (German: substitute) fuels. F-T production accounted for an estimated 9% of German war production of fuels and 25% of the automobile fuel.[5]

The United States Bureau of Mines, in a program initiated by the Synthetic Liquid Fuels Act, employed seven Operation Paperclip synthetic fuel scientists in a Fischer-Tropsch plant in Louisiana, Missouri in 1946.[8][5]

In Britain, Alfred August Aicher obtained several patents for improvements to the process in the 1930s and 1940s.[9] Aicher's company was named Synthetic Oils Ltd. (There is no connection with the Canadian company of the same name.)

Commercialization

Fluidized Bed Gasification with FT-pilot in Güssing, Burgenland, Austria

The F-T process has been applied on a large scale in some industrial sectors, although its popularity is hampered by high capital costs, high operation and maintenance costs, the uncertain and volatile price of crude oil, and environmental concerns. In particular, the use of natural gas as a feedstock only becomes practical when using "stranded gas", i.e. sources of natural gas far from major cities which are impractical to exploit with conventional gas pipelines and LNG technology; otherwise, the direct sale of natural gas to consumers would become much more profitable. Several companies are developing the process to enable practical exploitation of so-called stranded gas reserves.

Sasol

The largest scale implementation of F-T technology are in a series of plants operated by Sasol in South Africa, a country with large coal reserves but lacking in oil. Sasol uses coal and now natural gas as feedstocks and produces a variety of synthetic petroleum products, including most of the country's diesel fuel.[10]

Shell Middle Distillate Synthesis

One of the largest implementations of F-T technology is in Bintulu, Malaysia. This Shell facility converts natural gas into low-sulfur diesel fuels and food-grade wax. The scale is 12.000 barrel/day.

Ras Laffan, Qatar

The new LTFT facility scheduled to commission in 2010 at Ras Laffan, Qatar is based on the Sasol technology, using cobalt catalysts at 230 °C. It includes the "Pearl GTL" plant, converting natural gas to petroleum liquids at a rate of 140,000 barrels/day, with additional production of 120,000 barrels of oil equivalent in natural gas liquids and ethane.

UPM (Finland)

In October 2006, Finnish paper and pulp manufacturer UPM announced its plans to produce biodiesel by Fischer–Tropsch process alongside the manufacturing processes at its European paper and pulp plants, using waste biomass resulted by paper and pulp manufacturing processes as source material.[11]

Other

In the US, some coal-producing states have invested in F-T plants. In Pennsylvania, Waste Management and Processors Inc. was funded by the state to implement F-T technology licensed from Shell and Sasol to convert so-called waste coal (leftovers from the mining process) into low-sulfur diesel fuel.[12][13]

Research developments

Choren Industries has built an FT plant in Germany.[14][15] A small US-based company, Rentech, focuses on converting nitrogen-fertiliser plants from using a natural gas feedstock to using coal or coke, and producing liquid hydrocarbons as a co-product.

U.S. Air Force certification

Syntroleum, a publicly traded US company (Nasdaq: SYNM) has produced over 400,000 gallons of diesel and jet fuel from the Fischer–Tropsch process using natural gas and coal at its demonstration plant near Tulsa, Oklahoma. Syntroleum is working to commercialize its licensed Fischer-Tropsch technology via coal-to-liquid plants in the US, China, and Germany, as well as gas-to-liquid plants internationally. Using natural gas as a feedstock, the ultra-clean, low sulfur fuel has been tested extensively by the US Department of Energy, the Department of Transportation. Most recently, Syntroleum has been working with the U. S. Air Force to develop a synthetic jet fuel blend that will help the Air Force to reduce its dependence on imported petroleum. The Air Force, which is the U.S. military's largest user of fuel, began exploring alternative fuel sources in 1999. On December 15, 2006, a B-52 took off from Edwards AFB, California for the first time powered solely by a 50-50 blend of JP-8 and Syntroleum's FT fuel. The seven-hour flight test was considered a success. The goal of the flight test program is to qualify the fuel blend for fleet use on the service's B-52s, and then flight test and qualification on other aircraft. The test program concluded in 2007. This program is part of the Department of Defense Assured Fuel Initiative, an effort to develop secure domestic sources for the military energy needs. The Pentagon hopes to reduce its use of crude oil from foreign producers and obtain about half of its aviation fuel from alternative sources by 2016.[16] With the B-52 now approved to use the FT blend, the C-17 Globemaster III, the B-1B, and eventually every airframe in its inventory to use the fuel by 2011.[16][17]

Carbon dioxide reuse

In 2009, chemists working for the U.S. Navy investigated Fischer-Tropsch for generating fuels using hydrogen by electrolysis of seawater. When combined with the dissolved carbon dioxide using a cobalt-based catalyst, this study produced mostly methane gas, but 30 per cent methane with the rest being short-chain hydrocarbons. Further refining of the hydrocarbons produced could potentially lead to the production of kerosene-based jet fuel.[18]

The abundance of CO2 makes seawater an attractive alternative fuel source. Scientists at the U.S. Naval Research Laboratory stated that, "although the gas forms only a small proportion of air – around 0.04 per cent – ocean water contains about 140 times that concentration".[18] Dorner presented the findings to the American Chemical Society on 16 August 2009, at the Marriott Metro Center in Washington DC.[19]

See also

References

  1. ^ US Fuel Supply Statistics Chart
  2. ^ Bruce C. Gates “Extending the Metal Cluster-Metal Surface Analogy” Angewandte Chemie International Edition in English, 2003, Volume 32, pp. 228 – 229. doi:10.1002/anie.199302281
  3. ^ P.L. Spath and D.C. Dayton. "Preliminary Screening — Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas", NREL/TP510-34929,December, 2003, pp. 95
  4. ^ Andrei Y. Khodakov, Wei Chu, and Pascal Fongarland “Advances in the Development of Novel Cobalt Fischer-Tropsch Catalysts for Synthesis of Long-Chain Hydrocarbons and Clean Fuels” Chemical Review, 2007, volume 107, pp 1692–1744. doi:10.1021/cr050972v
  5. ^ a b c Leckel, D., "Diesel Production from Fischer-Tropsch: The Past, the Present, and New Concepts", Energy Fuels, 2009, volume 23, 2342-2358. doi:10.1021/ef900064c
  6. ^ Oliver R. Inderwildi, Stephen J. Jenkins, David A. King (2008). "Mechanistic Studies of Hydrocarbon Combustion and Synthesis on Noble Metals". Angewandte Chemie International Edition 47: 5253. doi:10.1002/anie.200800685. 
  7. ^ http://www.fischer-tropsch.org/primary_documents/patents/US/us1746464.pdf
  8. ^ German Synthetic Fuels Scientist
  9. ^ E.g. British patent no. 573,982, applied 1941, published 1945"Improvements in or relating to Methods of Producing Hydrocarbon Oils from Gaseous Mixtures of Hydrogen and Carbon Monoxide" (pdf). January 14, 1941. http://www.fischer-tropsch.org/primary_documents/patents/GB/gb573982.pdf. Retrieved 2008-11-09. 
  10. ^ "technologies & processes" Sasol
  11. ^ "UPM-Kymmene says to establish beachhead in biodiesel market", NewsRoom Finland
  12. ^ "Governor Rendell leads with innovative solution to help address PA energy needs", State of Pennsylvania
  13. ^ "Schweitzer wants to convert Otter Creek coal into liquid fuel", Billings Gazette, August 2, 2005, accessed August 13, 2007
  14. ^ Choren official web site
  15. ^ Fairley, Peter. Growing Biofuels - New production methods could transform the niche technology. MIT Technology Review November 23, 2005
  16. ^ a b Zamorano, Marti (2006-12-22). "B-52 synthetic fuel testing: Center commander pilots first Air Force B-52 flight using solely synthetic fuel blend in all eight engines". Aerotech News and Review. 
  17. ^ "C-17 flight uses synthetic fuel blend". 2007-10-25. http://www.af.mil/news/story.asp?id=123073293. Retrieved 2008-02-07. 
  18. ^ a b Kleiner, Kurt (18 August 2009). "How to turn seawater into jet fuel". New Scientist. http://www.newscientist.com/article/dn17632-how-to-turn-seawater-into-jet-fuel.html. Retrieved 2009-08-20. 
  19. ^ "FUEL 18 - Catalytic CO2 hydrogenation to feedstock chemicals for jet fuel synthesis.". American Chemical Society. http://oasys2.confex.com/acs/238nm/techprogram/P1260309.HTM. Retrieved 2009-08-20. 

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Contents

English

Wikipedia-logo.png

Wikipedia

Etymology

From Franz Fischer and Hans Tropsch, german chemists.

Proper noun

Singular
Fischer-Tropsch process

Plural
-

Fischer-Tropsch process

  1. (organic chemistry) The synthesis of hydrocarbons by the catalytic hydrogenation of carbon monoxide.

Translations

See also


Simple English

The Fischer–Tropsch process (or Fischer–Tropsch Synthesis) is a set of chemical reactions that turn a mixture of carbon monoxide gas and hydrogen gas into liquid hydrocarbons (fossil fuels like gasoline or kerosene). The F-T process has received attention for many different reasons, like a way to make diesel low in sulfur.

Contents

Process chemistry

The Fischer–Tropsch process involves a lot of reactions, which lead to both wanted and unwanted results. The good reactions create chemicals called alkanes. Sometimes the gas methane (natural gas) is made, but usually people do not want this gas. Sometimes different kinds of alcohol are produced in small amounts.

Other reactions relevant to FT

To make the gases needed for the F-T process, it takes many steps. For example, all chemicals going into the reactor must have all sulfur removed. For factories that start out with methane and want to make a liquid hydrocarbon (like kerosene), another important reaction is "steam reforming", which turns the methane into CO (carbon monoxide) and H2 (hydrogen gas). This is the science equation for how steam reforming works.

   2 H2O + CH4 → CO + 3 H2

It says, 2 molecules of H20 (steam) plus 1 molecule of CH4 (methane) turns into 1 molecule of C0(carbon monoxide) and 3 molecules of H2(hydrogen gas).

Fischer-Tropsch catalysts

A catalyst is a chemical you add to a process to make it go faster or speed it up. Many different catalysts can be used for the Fischer–Tropsch process. The most common catalysts are the metals cobalt, iron, and ruthenium. These metals are all transition metals. The metal nickel can also be used, but this is usually bad. If someone uses nickel, the reaction usually makes a lot of methane. Usually people do not want a lot of methane to be made.

Cobalt seems to be the most active catalyst(it has the biggest and fastest effect on the process). Cobalt catalysts are very good for the Fischer-Tropsch process when what you are putting in is natural gas. Iron catalysts are better for when the stuff you put in is lower quality (less pure) such as coal or biomass.

Most metals used for this process (like Cobalt, Nickel, and Rubenium) stay metal when you add them to the process. Iron catalysts are very different. Many times, iron catalysts change very much and form many chemical phases, like various oxides and carbides, during the reaction. It is important to control all of these reactions of the iron during the process, or else the process might not work.

Fischer-Tropsch catalysts are famous for being very, very sensitive to adding a little bit of sulfur. A tiny amount of sulfur can mess up the reactions. Cobalt is more sensitive to sulfur than iron.

Gasification

Gasification is turning things into gas. Some F-T factories that use coal, biomass or something else solid to start. Before these factories can start the process, they must turn the solids into gases like CO, H2, and alkanes. This process is called gasification. The gas collected from coal gasification often has a CO/H2 ratio of ~0.7 instead of the best ratio of ~2. People can adjust this ratio from 0.7 to 2.0 using the water-gas-shift-reaction.Gasification is a dirty and expensive process. Coal-based Fischer–Tropsch factories are factories that start out with coal, use gasification on it, then use the gas for the Fischer-Tropsch process. These factories can produce lots and lots of CO2. A big reason for this is because it takes very much energy to do the gasification process on the coal.

History

The original process was invented by Franz Fischer and Hans Tropsch. They were working at the Kaiser Wilhelm Institute in the 1920s, when they invented it. Since then many changes have been made to make it better. The term "Fischer-Tropsch" now is used for many processes that are like the original one. Fischer and Tropsch made lots of patents, like US patent no. 1,746,464, applied 1926, published 1930.[7] It was given to the factories in Germany in 1936.Germany had lots of coal but very little petroleum. The F-T process lets people change coal into gasoline, which is important to run cars and airplanes. Because of this, the FT-process was used by Nazi Germany and Japan during World War II to produce substitute fuels for tanks and cars. F-T production of fuel was about 9% of German war production of fuels and 25% of the automobile fuel.[5]

The United States Bureau of Mines, in a program started by the Synthetic Liquid Fuels Act, hired seven fuel scientists from Operation Paperclip in a Fischer-Tropsch plant in Louisiana, Missouri in 1946.[8][5]Operation Paperclip was a plan to get German scientists to work for the US during World War II.

Commercialization

Fluidized Bed Gasification with FT-pilot in Güssing, Burgenland, Austria

The F-T process has been used on by big companies, but it is sometimes un popular for many reasons. One is that it takes lots of money to buy equipment to get F-T factories to work. It also take lots of money to keep it running and to fix problems with it. Also, the cost of petroleum is very hard to predict. Usually, the factories only make money when they have access to "stranded gas". "Stranded gas" is what they call sources of natural gas very far from major cities, that takes too much money or resources to pump natural gas to the city. If they could just pump it to the city and sell the natural gas, they could make much more money. the direct sale of natural gas to consumers would become much more profitable. Several companies are developing the process to enable practical exploitation of so-called stranded gas reserves.

Sasol

The biggest F-T factories with the biggest use of F-T technology are owned and operated by the company Sasol in South Africa. South Africa is a country with lots of coal but not enough oil, just like Germany. Sasol takes coal and natural gas and uses them for the F-T Process. They produce many different substitutes for oil products, and produce most of the country's diesel fuel.[10]

Shell Middle Distillate Synthesis

One of the largest uses of F-T technology is in Bintulu, Malaysia. This Shell factory turns natural gas into low-sulfur diesel fuels and food-grade wax. They make 12,000 barrels/day.

In October 2006, Finnish paper and pulp manufacturer UPM announced its plans to produce biodiesel by Fischer–Tropsch process. It said that it will do this along with the manufacturing processes at its European paper and pulp plants. It will use the waste biomass, from paper and pulp manufacturing processes, as the material to turn into biodiesel.[11]

Research developments

Carbon dioxide reuse

In 2009, chemists working for the U.S. Navy studied Fischer-Tropsch for making fuels with hydrogen and electrolyzing seawater. This study produced mostly methane gas, but the rest were short-chain hydrocarbons. Further refining of the hydrocarbons produced could lead to making kerosene-based jet fuel.[18]

The abundance of CO2 makes seawater look like a good different fuel source. Scientists at the U.S. Naval Research Laboratory said that, "although the gas forms only a small proportion of air – around 0.04 per cent – ocean water contains about 140 times that concentration".[18]

References

  1. ^ US Fuel Supply Statistics Chart
  2. ^ Bruce C. Gates “Extending the Metal Cluster-Metal Surface Analogy” Angewandte Chemie International Edition in English, 2003, Volume 32, pp. 228 – 229. doi:10.1002/anie.199302281
  3. ^ P.L. Spath and D.C. Dayton. "Preliminary Screening — Technical and Economic Assessment of Synthesis Gas to Fuels and Chemicals with Emphasis on the Potential for Biomass-Derived Syngas", NREL/TP510-34929,December, 2003, pp. 95
  4. ^ Andrei Y. Khodakov, Wei Chu, and Pascal Fongarland “Advances in the Development of Novel Cobalt Fischer-Tropsch Catalysts for Synthesis of Long-Chain Hydrocarbons and Clean Fuels” Chemical Review, 2007, volume 107, pp 1692–1744. doi:10.1021/cr050972v
  5. ^ a b c Leckel, D., "Diesel Production from Fischer-Tropsch: The Past, the Present, and New Concepts", Energy Fuels, 2009, volume 23, 2342-2358. doi:10.1021/ef900064c
  6. ^ Oliver R. Inderwildi, Stephen J. Jenkins, David A. King (2008). "Mechanistic Studies of Hydrocarbon Combustion and Synthesis on Noble Metals". Angewandte Chemie International Edition 47: 5253. doi:10.1002/anie.200800685. 
  7. ^ http://www.fischer-tropsch.org/primary_documents/patents/US/us1746464.pdf
  8. ^ German Synthetic Fuels Scientist
  9. ^ E.g. British patent no. 573,982, applied 1941, published 1945"Improvements in or relating to Methods of Producing Hydrocarbon Oils from Gaseous Mixtures of Hydrogen and Carbon Monoxide" (pdf). January 14, 1941. http://www.fischer-tropsch.org/primary_documents/patents/GB/gb573982.pdf. Retrieved 2008-11-09. 
 10. ^ "technologies & processes" Sasol
 11. ^ "UPM-Kymmene says to establish beachhead in biodiesel market", NewsRoom Finland
 12. ^ "Governor Rendell leads with innovative solution to help address PA energy needs", State of Pennsylvania
 13. ^ "Schweitzer wants to convert Otter Creek coal into liquid fuel", Billings Gazette, August 2, 2005, accessed August 13, 2007
 14. ^ Choren official web site
 15. ^ Fairley, Peter. Growing Biofuels - New production methods could transform the niche technology. MIT Technology Review November 23, 2005
 16. ^ a b Zamorano, Marti (2006-12-22). "B-52 synthetic fuel testing: Center commander pilots first Air Force B-52 flight using solely synthetic fuel blend in all eight engines". Aerotech News and Review. 
 17. ^ "C-17 flight uses synthetic fuel blend". 2007-10-25. http://www.af.mil/news/story.asp?id=123073293. Retrieved 2008-02-07. 
 18. ^ a b Kleiner, Kurt (18 August 2009). "How to turn seawater into jet fuel". New Scientist. http://www.newscientist.com/article/dn17632-how-to-turn-seawater-into-jet-fuel.html. Retrieved 2009-08-20. 
 19. ^ "FUEL 18 - Catalytic CO2 hydrogenation to feedstock chemicals for jet fuel synthesis.". American Chemical Society. http://oasys2.confex.com/acs/238nm/techprogram/P1260309.HTM. Retrieved 2009-08-20.


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