Fischer-Tropsch reactions, modified

The mannitol-modified catalyst showed significantly increased activity in the Fischer-Tropsch reaction (Table 1.3). After 20 h on stream, the mannitol-modified catalyst is 286% as active as the unmodified catalyst, and 262% as active after 100 h. The selectivity values of the catalysts are similar. Hence, the characteristics of a mannitol-modified catalyst are that it has a higher activity than but the same selectivity as an unmodified catalyst. Increased activity for the FT reaction... 

Modification of the zeolite appears to have affected the selectivity of Ru in these hydrogenation reactions. Exchange of K cations for Na cations in Y zeolite increases the basicity of the support (ref. 9). In Fischer-Tropsch reactions over similar catalysts, Ru/Y catalysts so modified yielded significant increases in the olefinic product fraction at the expense of paraffins. Olefins are believed to be primary products in F-T synthesis, with paraffins being produced from olefins in secondary hydrogenation reactions. In an analogous fashion, the Ru/KY catalyst used in the present study might also be expected to... 

The intrinsic nature of tungsten carbide catalyst in CO-H2 reactions is to form hydrocarbons. This property can be modified by oxidic promoters as for the case of noble metals like Pt or Rh or by the presence of carbon vacancies at the surface. To increase the production of alcohols in the Fischer-Tropsch reaction, the catalyst should be bifunctional, with oxidic and carbidic components as in the case of WC on Ti02. Overcarburization of WC on supports like Si02 or Zr02 where the W-O-metal interaction is weak leads to C/W ratios close to unity and does not result in alcohol formation. 

Table VIII. MODIFIED FISCHER TROPSCH REACTIONS Ethylene Incorporation...

It has been found that the presence of Lewis acids or protons can accelerate carbonyl insertion reactions, providing another possibility of modifying catalysts. Mixtures of transition metal carbonyls and Lewis acids could in future be of interest as catalysts for CO hydrogenation, for example, in Fischer-Tropsch reactions (Eq. 2-82) [Til]. 

Liu Z, Li X, Asami K, Fujimoto K Iso-paraffins synthesis from modified Fischer-Tropsch reaction-insights into pd/beta and pt/beta catalysts, Catal Today 104(1) 41-47, 2005. 

Fischer-Tropsch A process for converting synthesis gas (a mixture of carbon monoxide and hydrogen) to liquid fuels. Modified versions were known as the Synol and Synthol processes. The process is operated under pressure at 200 to 350°C, over a catalyst. Several different catalyst systems have been used at different periods, notably iron-zinc oxide, nickel-thoria on kieselgtihr, cobalt-thoria on kieselgiihr, and cemented iron oxide. The main products are C5-Cn aliphatic hydrocarbons the aromatics content can be varied by varying the process conditions. The basic reaction was discovered in 1923 by F. Fischer and... 

Backgroxmd. Otto Roelen of Ruhrchemie, Germany, was chiefly responsible for development of the Oxo process. Some early work by Smith and his coworkers at the U.S. Bureau of Mines in 1930 had indicated that an increased yield of oxygenated compounds, as compared with conventional fischer-Tropsch practice, was obtmned when ethylene was added to water gas in the presence of cobalt catalyst at 200-225 C and atmospheric pressure. Roelen modified the operating conditions significantly and found that, at temperatures below 200°C "and pressures of 100-200 atm, all liquid products from the reaction of ethylene and water gas were oxygenated. He showed that the reaction could be applied generally to the formation of aldehydes from olefins and filed patents on the process as early as 1938. ... 

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