Test data, Fischer-Tropsch

ICP) measurements. The catalytic performance of the nanocatalysts was finally tested in the Fischer-Tropsch synthesis carried out in a fixed bed reactor. The obtained results were compared with literature data of commercially used Fischer-Tropsch catalysts. 

In this chapter a two a selectivity model is proposed that is based on the premise that the total product distribution from an Fe-low-temperature Fischer-Tropsch (LIFT) process is a combination of two separate product spectrums that are produced on two different surfaces of the catalyst. A carbide surface is proposed for the production of hydrocarbons (including n- and iso-paraffins and internal olefins), and an oxide surface is proposed for the production of light hydrocarbons (including n-paraffins, 1-olefins, and oxygenates) and the water-gas shift (WGS) reaction. This model was tested against a number of Fe-catalyzed FT runs with full selectivity data available and with catalyst age up to 1,000 h. In all cases the experimental observations could be justified in terms of the model proposed. 

Fischer-Tropsch synthesis data for catalysts A and B, as tested under realistic reactor... 

The fomation of carbon on iron and iron-copper catalysts by the reaction 2C0 = C02+C has been studied by several investigators (70-73). The most significant result of this work (in so far as the Fischer-Tropsch synthesis is concerned) is the fact that neither an iron-free nor a copper-free carbon deposit was obtained. The data show that cai-bon is deposited in the crystal lattice of the catalyst and the inability to obtain a copper-free carbon deposit from tests with an iron-copper catalyst shows that iron carbonyl formation will not explain the results. It is very probable that carbon is formed from carbon monoxide b3 way of iron carbide as an intermediate. Carbidic carbon diffuses rapidly throughout the crystal lattice and subsequently decomposes to yield elemental carbon, thus disrupting the lattice structure. 

Fischer-Tropsch activity, selectivity and deactivation data obtained in fixed bed reaction tests of Co/Si02 catalysts are summarized in Table 1. The turnover frequencies (TOFs) or site time yields based on H2 uptake and on rate measured after 20 hours of reaction agree within a factor of two with those reported for other cobalt catalysts [2, 3, 25-27]. CO conversion and methane selectivity versus time for Cab-O-Sil supported cobalt at both low and high space velocities are shown in Figure 1. It can be seen that at high conversion the catalyst deactivates rapidly while at low conversion the catalyst appears to be stable. The conversion is proportional to the water partial pressure thus water could be causing this deactivation. 

Selectivities. Hydrocarbon selectivity data were treated to test conformance to Schulz-Flory polymerization kinetics as outlined by Henrici-Olive and Olive (7) for Fischer-Tropsch catalysis. The pertinent correlation is ... 

The conversion data (reported in Fig. 5 as the time required to obtain a 90% conversion of acetophenone) for Pd/C catalysts prepared with and without ultrasoimd have been compared to the data, obtained in the same plant and with the same operating conditions, from two commercial samples, a sample (1) characterized by an eggshell metal distribution and a second one (2) characterized by a penetrated metal distribution. All the samples, both commercial and prepared in the laboratory, have the same metal loading (5% Pd wt/wt) and are supported on the same kind of active carbon. The sonicated sample shows a higher activity than all the catalysts tested, both in Fischer-Tropsch synthesis and in the hydrogenation of acetophenone. 

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