Tropsch synthesis, Fisher

The mixture of carbon monoxide and hydrogen is enriched with hydrogen from the water gas catalytic (Bosch) process, ie, water gas shift reaction, and passed over a cobalt—thoria catalyst to form straight-chain, ie, linear, paraffins, olefins, and alcohols in what is known as the Fisher-Tropsch synthesis. 

Iglesia, E. 1997. Design, synthesis, and use of cobalt-based Fisher-Tropsch synthesis catalyst. Appl. Catal. 161 59-78. 

Zhang, Y., Li, Y., Yang, G., Sun, S., and Tsubaki, N. 2007. Effects of impregnation solvent on Co/Si02 catalyst for Fisher-Tropsch synthesis A highly active and stable catalyst with bimodal sized cobalt particle. Appl. Catal. A Gen. 321 79-85. 

Figure 4. Differential spectra of CO chemisorbed on alumina-supported Ni particles both before and after heating to 425 K. Very little surface hydrocarbon is seen to form on the Ni particles. This lack of surface hydrocarbon reflects the selectivity of such catalysts for methanation over Fisher-Tropsch synthesis.

Fuel gas for gas turbines (IGCC) and as a replacement for natural gas or chemical substitute. Can be used as a feedstock to Fisher-Tropsch synthesis, methanation, methanol, and ammonia production. 

H2 has many uses in hydrogenation, and CO has many uses in carbonylation. The mixture is used in methanol synthesis and in the Fisher Tropsch synthesis of hydrocarbons. 

We next return to another reaction of a CO + H2 mixture, which we called synthesis gas or syngas. It has this name because it is used to synthesize many chemicals such as methanol. Another synthesis reaction from CO and H2 is a polymerization process called the Fisher Tropsch synthesis of synthetic diesel fuel. 

In Fisher Tropsch synthesis from CO and H2, different catalysts produce different types of product molecules. Referring to the figure of propagation in the FT process, sketch the termination steps that will lead to (a) alkanes, (b) a-olefms, and (c) alcohols. 

In contrast to the Fisher Tropsch synthesis of higher alkanes from CO and H2, Ni catalysts produce primarily methane, and Cu/ZnO catalysts produce mainly methanol. Sketch the mechanistic steps that favor these products rather than polymerization ... 

It has been reported that for diameters less than 7.62 cm, the gas holdup depends on the column diameter, whereas it is independent of it for diameters greater than 10.2 cm (Hughmark, 1967 Saxena, 1991). The same has been found in studies of the Fisher-Tropsch synthesis in slurry bubble columns, where it has been reported that the effect of the column diameter is negligible when foam is not present in the system (Fox and Degen, 1990). 

Cobalt is a good catalyst for hydrogenation reactions it is used in the synthesis of low molecular weight hydrocarbons and for the conversion of nitriles in primary amines [37]. It can as well be applied in Fisher-Tropsch synthesis [30], The structure of cobalt is HCP (see Figure 2.6) and the electronic arrangement of Co is [Ar]3d74s2]. 

Poisoning of transition metals by sulfur is a serious problem encountered in many industrial processes [1-4]. In the Fisher-Tropsch synthesis of hydrocarbons from CO/H2 mixtures, the presence of a few ppm volume ratio of a sulfur containing gas can have a drastic effect on the life time of an iron catalyst [1]. On the other hand, a partial and well controlled treatment of a metal by sulfur can result in desirable effects, particularly with regard to the manipulation of catalyst selectivity for certain reactions [5]. 

Fisher-Tropsch synthesis 1938 Fuels CO -b H2 — paraffins Fe or Co with promoters on support... 

Example 10-1 Turnover Frequency in Fisher-Tropsch Synthesis CO + SHj ------------------------------> CH4 + H2O... 

The Fisher-Tropsch synthesis was studied using a commercial 0.5 wt % Ru on 7-AI2O3. The catalyst dispersion percentage of atoms exposed, determined from hydrogen chemisorption, was formd to be 49%. At a pressure of 988 kPa and a temperature of 475 K, a turnover frequency of 0.044 s was reported for methane. What is thie rate of formation of methane in mol/s g of catalyst (metal plus support) ... 

Alloy surfaces are of substantial importance in catalysis, such as in the hydrogenation of unsaturated hydrocarbons, Fisher-Tropsch synthesis, steam reforming of methane, and many other processes [41]. In electrocatalysis, they have recently received attention in relation to the development of CO-tolerant fuelcell catalysts [42]. In many of these processes, atomic hydrogen and carbon monoxide are the most important intermediates or poisons therefore, these two adsorbates have received a great deal of attention in theoretical and computational studies. 

Migratory insertion of CO into a transition metal-hydride bond is not common. Nevertheless, its importance in catalytic reactions such as the Fisher-Tropsch synthesis has attracted much attention T The marked difference in behavior between metal alkyls and metal hydrides with respect to the insertion of CO is largely a consequence of thermodynamic factors ... 

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