Nickel-thoria catalyst

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... 

Nickel-kieselguhr catalysts with or without a small percentage of magnesia and thoria These catalysts were prepared by precipitation of the metals as carbonates from the solutions of their nitrates holding a suspension of B.D.H. kieselguhr. The carbonates were subsequently decomposed to the oxides in a current of air and the nickel reduced by hydrogen at 300°. 

The exchange of methane with deuterium has been followed on nickel films 12), on a cobalt-thoria Fischer-Tropsch catalyst 13) and on films of rhodium, platinum, palladium, and tungsten 30). The important features of the exchange over the metal films may be summarized as follows ... 

Historical Development and Future Perspectives The Fischer-Tropsch process dates back to the early 1920s when Franz Fischer and Hans Tropsch demonstrated the conversion of synthesis gas into a mixture of higher hydrocarbons, with cobalt and iron as a catalyst [35, 36], Some 20 years earlier, Sabatier had already discovered the reaction from synthesis gas to methane catalyzed by nickel [37]. The FTS played an important role in the Second World War, as it supplied Germany and Japan with synthetic fuel. The plants used mainly cobalt catalysts supported on a silica support called kieselguhr and promoted by magnesia and thoria. 

Precipitation-deposition can be used to produce catalysts with a variety of supports, not only those that are formed from coprecipitated precursors. It has been employed to prepare nickel deposited on silica, alumina, magnesia, titania, thoria, ceria, zinc oxide and chromium oxide.36 It has also been used to make supported precious metal catalysts. For example, palladium hydroxide was precipitated onto carbon by the addition of lithium hydroxide to a suspension of... 

To obtain good conversion by reaction (4) even with an excess of steam It is necessary to use an active catalyst in order to operate at a temperature lower than 1000° C. Nickel catalysts, promoted with alumina or thoria and supported on fire clay, magnesium oxide, or brick, are very suitable for the process, giving essentially equilibrium conversion at low rates of gas flow through the converter. At increasing rates of flow the increase in unconverted methane is practically linear with the increase in space velocity. ... 

Nickel, cobalt, and iron catalysts are cmnmonly used for the Fischer-Tropsch s thesis. Nickel catalysts have been prepared by precipitation from a nitrate solution with potassium carbonate in the presence of thoria and kieselguhr in the proportions lOONiilSThOzilOO kieselguhr. It is not desirable to employ nickel catalysts at low temperatures and elevated pressures because the formation of nickel carbonyl is excessive. In the temperature range of 170-220°C at. low pressures, both liquid and gaseous products are obtained. As the temperature is increased to 300-350°C and the pressure increased to 300-400 psi, nickel catalysts produce only methane. Thus, these catal nsts can be used for making a gas from coal comparable in heating value to natural gas. 

The first promising catalyst was introduced by 1931 and contained a high proportion of nickel oxide supported on a mixture of thoria and kieselguhr. The convention widely used at the time was to describe composition as 100 parts nickel, 18 parts thoria, 100 parts kieselguhr. Catalysts made with cobalt rather than nickel were more effective but could not be considered eommercially at that time because cobalt was not available in suffieiently large quantities. The same problem had, of course, faced Haber and Boseh in the replaeement of osmium by iron oxide for the ammonia synthesis eatalyst. 

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