From Fischer-Tropsch process

As a constituent of synthesis gas, hydrogen is a precursor for ammonia, methanol, Oxo alcohols, and hydrocarbons from Fischer Tropsch processes. The direct use of hydrogen as a clean fuel for automobiles and buses is currently being evaluated compared to fuel cell vehicles that use hydrocarbon fuels which are converted through on-board reformers to a hydrogen-rich gas. Direct use of H2 provides greater efficiency and environmental benefits. ... 

In summary, we have shown that by pyrolyzing waste polymers such as polyethylene, waxy products similar to those from Fischer-Tropsch processing can be made, which can then be converted to high-quality lubricant oils via wax hydroisomerization. While a detailed economic analysis has not yet been carried out, the much higher value of lube oil relative to transportation fuels suggests that this may be a more viable and profitable way of disposing of waste plastic, a growing waste stream problem. 

Weller and Friedel (83) Isomere distribution in hydrocarbons from Fischer-Tropsch process. 

Important unfunctionalized acyclic alkenes used in industry are ethene (C2) and propene (C3), isomeric butenes (C4), octenes (Cg), and olefins up to a chain length of C g. In general, a distinction is made between short-chain (C3, C4), medium-chain (C5-C42), and long-chain (C13-C19) 0x0 products. Some linear a-olefins (LAOs), such as 1-butene, 1-hexene, 1-octene, or 1-decene, can be extracted selectively from Fischer- Tropsch processes. As exemplarily conducted in Sasol s SYNTHOL process, a range of olefins with a broad distribution of odd and even carbon numbers can be obtained [9, 10]. In the case of low-cost ethylene, dimerization may produce 1-butene. Trimerization or tetramerization produces 1-hexene and/or 1-octene [11]. 

Fischer-Tropsch Process. The Hterature on the hydrogenation of carbon monoxide dates back to 1902 when the synthesis of methane from synthesis gas over a nickel catalyst was reported (17). In 1923, F. Fischer and H. Tropsch reported the formation of a mixture of organic compounds they called synthol by reaction of synthesis gas over alkalized iron turnings at 10—15 MPa (99—150 atm) and 400—450°C (18). This mixture contained mostly oxygenated compounds, but also contained a small amount of alkanes and alkenes. Further study of the reaction at 0.7 MPa (6.9 atm) revealed that low pressure favored olefinic and paraffinic hydrocarbons and minimized oxygenates, but at this pressure the reaction rate was very low. Because of their pioneering work on catalytic hydrocarbon synthesis, this class of reactions became known as the Fischer-Tropsch (FT) synthesis. 

The Fischer-Tropsch process can be considered as a one-carbon polymerization reaction of a monomer derived from CO. The polymerization affords a distribution of polymer molecular weights that foUows the Anderson-Shulz-Flory model. The distribution is described by a linear relationship between the logarithm of product yield vs carbon number. The objective of much of the development work on the FT synthesis has been to circumvent the theoretical distribution so as to increase the yields of gasoline range hydrocarbons. 

Fig. 1. Routes to Hquid fuels from natural gas and coal via synthesis gas. F-T is the Fischer-Tropsch process.

The second reaction is called the Fischer-Tropsch synthesis of hydrocarbons. Depending on the conditions and catalysts, a wide range of hydrocarbons from very light materials up to heavy waxes can be produced. Catalysts for the Fischer-Tropsch reaction iaclude iron, cobalt, nickel, and mthenium. Reaction temperatures range from about 150 to 350°C reaction pressures range from 0.1 to tens of MPa (1 to several hundred atm) (77). The Fischer-Tropsch process was developed iadustriaHy under the designation of the Synthol process by the M. W. Kellogg Co. from 1940 to 1960 (83). 

Sasol Fischer-Tropsch Process. 1-Propanol is one of the products from Sasol s Fischer-Tropsch process (7). Coal (qv) is gasified ia Lurgi reactors to produce synthesis gas (H2/CO). After separation from gas Hquids and purification, the synthesis gas is fed iato the Sasol Synthol plant where it is entrained with a powdered iron-based catalyst within the fluid-bed reactors. The exothermic Fischer-Tropsch reaction produces a mixture of hydrocarbons (qv) and oxygenates. The condensation products from the process consist of hydrocarbon Hquids and an aqueous stream that contains a mixture of ketones (qv) and alcohols. The ketones and alcohols are recovered and most of the alcohols are used for the blending of high octane gasoline. Some of the alcohol streams are further purified by distillation to yield pure 1-propanol and ethanol ia a multiunit plant, which has a total capacity of 25,000-30,000 t/yr (see Coal conversion processes, gasification). 

Medium Pressure Synthesis. Pressures of 500—2000 kPa (5—20 atm) were typical for the medium pressure Fischer-Tropsch process. Cobalt catalysts similar to those used for the normal pressure synthesis were typically used at temperatures ranging from 170 to 200°C ia tubular "heat exchanger" type reactors. 

Development of SASOL. Over 70% of South Africa s needs for transportation fuels are being suppHed by iadirect Hquefaction of coal. The medium pressure Fischer-Tropsch process was put iato operation at Sasolburgh, South Africa ia 1955 (47). An overall flow schematic for SASOL I is shown ia Figure 12. The product slate from this faciUty is amazingly complex. Materials ranging from hydrocarbons through oxygenates, alcohols, and acids are all produced. 

The Fischer-Tropsch process has attracted renewed interest as a way to produce high quality, sulfur-free diesel fuel from natural gas and, possibly, an opportunity to utilize natural gas at remote oilfields. The process represents proven technology and is regarded as an alternative for when oil may no longer be widely available, and one has to resort to natural gas and coal. In a really futuristic scenario one may even contemplate the use of GO and H2 produced by photo-catalytic dissociation of GO2 and water. 

The Fischer-Tropsch process has recently received renewed attention due to the increasing demand and rising costs of fuels. Fischer-Tropsch processes are either coal based or methane based. Coal-based processes face serious issues in terms of the increasing regulations regarding limiting C02 emissions worldwide. There is a firm need for innovative and novel solutions for dealing with C02 emissions from the CTL process. 

LTFT syncrude is more difficult to refine to on-specification transportation fuels, but has become almost synonymous with distillate production from Fischer-Tropsch-based GTL conversion. In this application the SMDS process has been the trailblazer. However, there are two potential misconceptions that should be pointed out. First, Fischer-Tropsch distillate produced from LTFT syncrude is... 

In view of the size of operation being contemplated, it is unlikely that homogeneous catalysts will play a primary role in the production of synthetic oil. However, from the standpoint of the chemical industry, the complex mixture of products obtained from the classical Fischer-Tropsch process is generally unattractive owing to the economic constraints imposed by costly separation/purification processes. What is needed is a catalyst system for the selective conversion of CO/H2 mixtures to added-... 

Because the synthesis gas produced from coal is generally relatively poor in hydrogen, a typical CO H2 ratio being ca. 1 1, and because, as can be seen from Eqs. (14) and (15), a hydrogen-rich gas is required for the production of hydrocarbons and chemicals, a hydrogen enrichment step is usually necessary for the Fischer-Tropsch process. 

Duftschmid A variation of the Fischer-Tropsch process in which synthesis gas and an oil are circulated over a fixed bed of iron catalyst in order to increase the yield of olefins from the gas. 

Kolbel-Rheinpreussen A process for converting syngas to gasoline. The gas was passed through a suspension of an iron catalyst in an oil. Developed by H. Kolbel at Rheinpreussen, Germany, from 1936 until the 1950s when it was supplanted by the Fischer-Tropsch process. 

Krupp-Kohlechemie A process for making hard paraffin wax from water gas by a variant of the Fischer-Tropsch process. The products were called Ruhrwachse. Developed by Ruhr Chemie and Lurgi Ges. fur Warmetechnie. 

Synthol A version of the Fischer-Tropsch process, for making liquid fuels and organic chemicals from syngas. Developed by Pullman Kellogg between 1940 and 1960. First operated at the SASOL plant in South Africa in 1955. The name was used also for the product from the original Fischer-Tropsch process, developed in the 1920s. See also Synol. Hydrocarbon Process., 1963, 42(11), 225. 

Another, highly selective oligomerisation reaction of ethene should be mentioned here, namely the trimerisation of ethene to give 1-hexene. Worldwide it is produced in a 0.5 Mt/y quantity and used as a comonomer for ethene polymerisation. The largest producer is BP with 40 % market share utilizing the Amoco process, formerly the Albemarle (Ethyl Corporation) process. About 25 % is made by Sasol in South Africa where it is distilled from the broad mixture of hydrocarbons obtained via the Fischer-Tropsch process, the conversion of syn-gas to fuel. The third important process has been developed by Phillips. 

In addition to this, solid acid catalysts can also be used in the hydroisomerization cracking of heavy paraffins, or as co-catalysts in Fischer-Tropsch processes. In the first case, it could also be possible to transform inexpensive refinery cuts with a low octane number (heavy paraffins, n-Cg 20) to fuel-grade gasoline (C4-C7) using bifunctional metal/acid catalysts. In the last case, by combining zeolites with platinum-promoted tungstate modified zirconia, hybrid catalysts provide a promising way to obtain clean synthetic liquid fuels from coal or natural gas. 

Fischer-Tropsch process (or synthesis). The manufacture of synthesis gas (carbon monoxide and hydrogen) by passing steam over hot coal and the subsequent production of organic compounds from the synthesis gas. 

Moreover, alkanes can also be produced from the reaction of reforming products, H2 and CO/CO2, via methanation and Fischer-Tropsch processes. 

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