Carbon dioxide Fischer-Tropsch process

Methanation is one of a more general class of Fischer-Tropsch processes in which carbon monoxide and carbon dioxide are hydrogenated to form various light hydrocarbons and water. Although the primary reaction using a nickel on alumina catalyst is the methanation of carbon monoxide, appreciable side reactions can occur in the methanation system. The reactions in the methanation system are shown in Table I and include carbon dioxide... 

Methane is the principal gas found with coal and oil deposits and is a major fuel and chemical used is the petrochemical industry. Slightly less than 20% of the worlds energy needs are supplied by natural gas. The United States get about 30% of its energy needs from natural gas. Methane can be synthesized industrially through several processes such as the Sabatier method, Fischer Tropsch process, and steam reforming. The Sabatier process, named for Frenchman Paul Sabatier (1854—1941), the 1912 Nobel Prize winner in chemistry from France, involves the reaction of carbon dioxide and hydrogen with a nickel or ruthenium metal catalyst C02 + 4H2 —> CH4 + 2H20. 

In the Fischer-Tropsch process the coal gasifier produces synthesis gas. This goes to water-gas shift and acid gas removal of carbon dioxide and hydrogen sulphide. The Fischer-Tropsch synthesis converts the synthesis gas into hydrocarbons (-[CH2]-) and water ... 

Removal of carbon monoxide and carbon dioxide by methanation is required for the protection of certain hydrogenation and ammonia synthesis catalysts against rapid deactivation. It is also necessary when the hydrogen is used in hydroprocessing operations because CO2 and CO can lead to temperature excursions and catalyst damage in the reactors. Furthermore, methanation is an essential step in the reaction systems associated with the Fischer-Tropsch synthesis and with the production of synthetic natural gas from liquid hydrocarbons and coal. Grayson (1956) presented a detailed discussion of methanation in connection with the Fischer-Tropsch process. 

The role of water also comes to the fore in the classical Synthol and Kogasin processes (/ oks Gas Benzm i.e., carbon —> gaseous products — gasoline) of Fischer and Tropsch, not least by virtue of the ubiquitous water-gas shift reaction following eq. (3), (cf. Section 3.2.11). It is obvious that the reducing action of water leads to a corresponding amount of carbon dioxide which is in equilibrium under the standard process conditions. 

Here we present evidence that this can be achieved in three different cases ethylene epoxidation, carbon dioxide methanation and Fischer-Tropsch synthesis [6], and demonstrate the advantages for ethylene epoxidation with a 2-D computer model of the process. Table 2 summarizes the rationale for selecting these processes as examples. Since the purpose was to demonstrate feasibility and advantage for foam-supported catalysts, no attempt was made to incorporate promoters to improve activity or selectivity. 

The reactions of carbon dioxide and water with carbonaceous species are well known reactions and have been employed in various chemical processes to control or remove unwanted carbonaceous material. The most important application is found in the gasification of coal, forming a mixture of hydrogen and carbon monoxide (syngas), which is also used in important industrial processes such as methanol synthesis and in the production of hydrocarbons (Fischer-Tropsch synthesis). In these reactions, alkali metal catalysts and promoters have been used extensively for their ability to activate water and carbon dioxide species, thus speeding up their reaction with carbon. Alkali metals are therefore a clear candidate for this study. A number of mechanisms have been suggested... 

The conversion of methane by carbon dioxide to form carbon monoxide and hydrogen is called dry reforming. Its strategic interest resides in the fact that it provides a CO/H2 ratio adapted to the gas-to-liquid process (methanol and Fischer-Tropsch synthesis of higher hydrocarbons). This reaction takes place on metals such as Rh/Si02, Co/Si02 or nickel-based catalysts. For these catalysts... 

Since the 1920s the Fisher-Tropsch process (see http //www.fischer-tropsch.org, accessed 22 June 2013) [26] is the one most commercially exploited as a route to hydrocarbons. Through gasification of biomass (or other carbon sources such as coal or natural gas) a synthesis gas (syngas) composed mainly of carbon monoxide, carbon dioxide and hydrogen can be produced. 

The chemical processes being used in the twenty-first century favor the indirect Fischer-Tropsch method of coal liquefaction. In this process, coal is initially subjected to very high heat to create a charred substance that can be combined with carbon dioxide and steam to produce a synthesis gas composed of hydrogen and carbon monoxide. The gas is then chemically subjected to a metallic catalyst, which transforms it into a synthetic crude oil. The resultant synthetic oil can then be refined into the desired fuel. 

Fischer-Tropsch fuels are those made artificially using the FT process. Basically a fuel such as biomass, or even natural gas, is steam reformed using the methods described in Chapter 8. The product hydrogen and carbon dioxide are then reacted, over catalysts developed by Fischer and Tropsch, to produce liquid fuels such as octane, C9H20, C10H22, etc. 

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