Fischer-Tropsch synthesis concentration

The formation of relatively stable vesicles did not require the presence of pure compounds mixtures of components could also have done the job. However, whether the concentrations of the compounds isolated from the Murchison meteorite would have been sufficient for the formation of prebiotic protocells or vesicles is unclear, even if concentration effects are assumed. Sequences in which the technical Fischer-Tropsch synthesis is the role model have been proposed as possible sources of amphiphilic building blocks. 

In case of Fischer-Tropsch synthesis, we have to consider that the first-order reaction rate constant is related to the concentration in the gas phase (e.g., ce2), and that the diffusive flux in the liquid-filled pores is related to the concentration in the liquid (ce21). Thus, instead of Equation 12.10, we have to use... 

Kim42,43 found higher CO conversion and higher C5+ and lower methane selectivities when external water was added (20 parts per 100 parts of 2 1 H2 CO feed) during Fischer-Tropsch synthesis. However, when the water concentration in the feed was higher than 28% the CO conversion decreased. 

It is also interesting that if the goal is to produce H2-CO gas mixtures, for instance in the Fischer-Tropsch synthesis, one needs to suppress the WGSR operating in the vapor phase or to operate at higher concentrations of the oxygenated reactant in water or to use a catalyst on which the rate of the WGSR is slow. 

Group II The activity drops more than the Ni surface concentration (Fig. 13), i.e., at least about 20 times. However, for several reactions this drop is two or more orders of magnitude. The reactions included in this group are methanation and Fischer-Tropsch synthesis, isomerization, de-hydrocyclization or hydrogenolysis of alkanes, ether formation from alcohols, metathesis of alkylamines, and possibly other reactions. 

Possible inter relationships of natural substances are important. Similarities of the low molecular weight alkane isomers from crude oil and Fischer-Tropsch synthesis product have been reported. A similar composition for high temperature coal carbonization has been found. The C4 to C7 alkane isomers from these sources can be calculated quantitatively with equations developed for Fischer-Tropsch products. A reversal of the concentrations of the monomethyl isomers from CG (2 Me > 3 Me) to C7 (3 Me > 2 Me) occurs in all three products comparisons at higher carbon numbers indicate some dissimilarities. Naphthene isomers for crude oil and high temperature coal carbonization also have similar compositions. Aliphatic hydrocarbons from low temperature coal processes are considerably different. The C1 isotopic composition of pure compounds from the various sources are being compared in order to provide information on their origin. 

Several workers (Kolbel et al. [40, 41], Deckwer et al. [17], Michael and Reicheit [42]) have investigated the heat transfer in BSCR versus solid concentration and particle diameters. Deckwer et al. [17] applied Kolmogoroff s theory of isotropic turbulence in combination with the surface renewal theory of Higbie [43] and suggested the following expression for the heat transfer coefficient in the Fischer-Tropsch synthesis in BSCR ... 

The transient response of the catalyst to a step function in the concentration of reactant gases is simulated from the kinetics of the Fischer-Tropsch synthesis. 

M. . Dry The Fischer-Tropsch Synthesis The fourth chapter concentrates mainly on the development of the Fischer-Tropsch process from the late 1950 s to 1979. During this period the Sasol plant was the only Fischer-Tropsch process in operation and hence a large part of this review deals with the information generated at Sasol. The various typesofreactors are comparedand discussed (198 references). 

In the design of upflow, three phase bubble column reactors, it is important that the catalyst remains well distributed throughout the bed, or reactor space time yields will suffer. The solid concentration profiles of 2.5, 50 and 100 ym silica and iron oxide particles in water and organic solutions were measured in a 12.7 cm ID bubble column to determine what conditions gave satisfactory solids suspension. These results were compared against the theoretical mean solid settling velocity and the sedimentation diffusion models. Discrepancies between the data and models are discussed. The implications for the design of the reactors for the slurry phase Fischer-Tropsch synthesis are reviewed. 

The vork described in this paper extends the understanding of solid concentration profiles in three phase huhhle column reactors, with emphasis on the Fischer-Tropsch synthesis, by ... 

The concentrations of hydrocarbons adsorbed in catalyst pores, especially of the heavier products, depend on their partial pressure in the catalyst bed. The partial pressure of the products at the same conversion and selectivity levels depends on the total pressure in the reactor. Therefore, Fischer-Tropsch synthesis at total pressure of 20 bar (tt CO=2) would result in a higher partial pressure of hydrocarbons. The higher partial pressure would lead to the condensation of reaction products which are normally in gaseous phase... 

CO reactants and the H2O product of the synthesis step inhibit many of these secondary reactions. As a result, their rates are often higher near the reactor inlet, near the exit of high conversion reactors, and within transport-limited pellets. On the other hand, larger olefins that are selectively retained within transport-limited pellets preferentially react in secondary steps, whether these merely reverse chain termination or lead to products not usually formed in the FT synthesis. In later sections, we discuss the effects of olefin hydrogenation, oligomerization, and acid-type cracking on the carbon number distribution and on the functionality of Fischer-Tropsch synthesis products. We also show the dramatic effects of CO depletion and of low water concentrations on the rate and selectivity of secondary reactions during FT synthesis. 

Within the Fischer-Tropsch research ECN Biomass concentrates on the definition of the gas cleaning with respect to the typical B R in urities, like NHj, HCl, HCN, H]S, COS, tars (heavy organic molecules), soot, and alkali metals, Traces (< ppm) of these compounds can already be a poison for the Fischer-Tropsch catalysts. For the implementation of B R and Fischer-Tropsch ECN its strategy is on the demonstration of integrated systems to reduce the time necessary to realise a first full-scale installation for conversion of biomass and residue, gas cleaning, and Fischer-Tropsch synthesis. To achieve this ECN focuses on two lines of development ... 

The behaviour of CO2 in Fischer-Tropsch synthesis was investigated using a promoted iron and a promoted cobalt catalyst. The decrease in yield of hydrocarbons is more pronounced on cobalt than on iron. The product distribution on iron remains nearly constant with increasing CO2 concentration, however on cobalt the selectivity to methane increases dramatically. 

We have recently studied the effect of water on the cobalt FT catalysts [2]. Water is the major oxygen containing product in Fischer-Tropsch synthesis (FTS), and in certain reactor types (e.g. backmixed slxnrry reactors) the concentration of water will be high and this can influence the catalyst surface. Water can deactivate the catalyst, and we have shown that this is mainly due to a surface reoxidation of cobalt. 

To investigate the role of readsorption and secondary conversion during Fischer-Tropsch synthesis, experiments were performed in which small amounts of ethylene were added to the synthesis gas before reaction. The fate of the olefin was then followed as a function of reaction time. In the case of ethylene (2.7 mol % in synthesis gas) under the present reaction conditions, 80-90% of the added olefin reacted. As shown in Figure 13, the predominant reaction was hydrogenation to ethane, but approximately 10% of the added ethylene was incorporated into growing chains. The incorporation of ethylene into chain products increased the relative amounts of C3 to C5 hydrocarbons as shown in Figure 14. To further demonstrate this effect, a series of experiments were performed in which the initial concentration of ethylene was varied while all other... 

The early work at Mellon concentrated on the Fischer-Tropsch synthesis reaction and was stimulated by a national concern for the dwindling supplies of petroleum, a concern which has stimulated the resurgence of interest in the Fischer-Tropsch synthesis in recent years. In carrying out this work. Professor Emmett introduced a new and important technique for the study of the mechanism of catalytic reactions. This was the use of... 

The Fischer-Tropsch synthesis leads almost exclusively to aliphatic hydrocarbons and oxygen compounds the proportion of aromatics depends on the type of reactor system used. The aromatics content of the gasoline and diesel oil produced by the fixed-bed process in the SASOL I plant is negligible, while the aromatics content of gasoUne produced by the fluidized-bed method by SASOL II and III is around 7%, and the level in diesel oil 10%. The increase in aromatics with the fluidized-bed reactor is a result of the reaction temperature, which is approximately 100 °C higher. Since the concentration is rather low, it is not economical to... 

By the example of various catalytic reactions (ethylene epoxidation over Ag, deNOx with methane on Co-ZSM-5, Fischer-Tropsch synthesis over Co-based systems), we show how the reaction mechanism was revealed and the concentrations of key intermediates and reaction rate coefficients were estimated using different isotope labels ( 0, etc.). A single instance... 

Since the discovery of the synthesis at the Kaiser Wilhelm Institute (Germany) in 1923 by Franz Fischer and Hans Tropsch, the kinetics of the Fischer-Tropsch synthesis have been studied extensively and many attempts have been made to describe the rate of reaction, either by using power law rate equations or equations based on certain mechanistic assumptions. In most cases, the rate of H2 and CO consumption is correlated with the (measurable) gas phase concentrations or partial pressures of H2, CO, and/or H2O. An overview of rate equations for iron catalysts is given by Huff and Satterfield (1984a) and for cobalt catalysts by Yates and Satterfield (1991). Details on the kinetics and reaction mechanism are, for example, discussed by Donnelly and Satterfield (1989), Dry (1982), Fernandes (2005), Huff and Satterfield (1984b), Post et al. (1989), Riedel et al. (1999), Schulz and Claeys (1999), Schulz et al. (1999), Van Steen and Schulz (1999), and Van Steen (1993). 

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