Iron-based catalysts experiment

A continuous cross-flow filtration process has been utilized to investigate the effectiveness in the separation of nano sized (3-5 nm) iron-based catalyst particles from simulated Fischer-Tropsch (FT) catalyst/wax slurry in a pilot-scale slurry bubble column reactor (SBCR). A prototype stainless steel cross-flow filtration module (nominal pore opening of 0.1 pm) was used. A series of cross-flow filtration experiments were initiated to study the effect of mono-olefins and aliphatic alcohol on the filtration flux and membrane performance. 1-hexadecene and 1-dodecanol were doped into activated iron catalyst slurry (with Polywax 500 and 655 as simulated FT wax) to evaluate the effect of their presence on filtration performance. The 1-hexadecene concentrations were varied from 5 to 25 wt% and 1-dodecanol concentrations were varied from 6 to 17 wt% to simulate a range of FT reactor slurries reported in literature. The addition of 1-dodecanol was found to decrease the permeation rate, while the addition of 1-hexadecene was found to have an insignificant or no effect on the permeation rate. 

The hydrogenation of atomic nitrogen (N- ) preadsorbed on an iron-based catalyst surface has been studied by Fastrup et al. [9]. For the sake of simplicity, the non-steady-state TPD cell during the TPSR experiment has been treated as a CSTR. In the present study, simulation results are shown using the proper PFR model. Additionally, experimental and simulation results obtained with a Cs-Ru/MgO catalyst are presented to illustrate the influence of the reactor model. 

Iron-based Catalysts. - As indicated above, iron-based compounds have been the choice materials for catalysis of the first stage of DCL viz. coal depolymerization. In a recent paper, Huffman et al. have used a variety of analytical techniques to determine the structures of a large number of nanoscale iron-based catalysts before and after DCL experiments. In most of these experiments using iron oxide and iron oxyhydride catalysts, the material found in the residue after the DCL experiments is pyrrhotite, formed by the reaction of H2S with FeS2 present in the coals and with the added catalyst. A number of these catalysts have been used by Pradhan et al. in DCL experiments and by Ibrahim and Seehra in ESR experiments. We now compare the results of these experiments, since they provide the most direct use of ESR spectroscopy to date in DCL experiments. 

In order to investigate the catalytic activity of Ru catalysts, and compare with iron catalyst, we choose the representative iron catalyst A301 with wiistite as precursor as the reference sample. A301 has the highest activity among all of the iron-based catalysts for ammonia synthesis and now it has been widely used in ammonia synthesis industry. In order to get the reliable and comparable data of the evaluation of catalytic activity, the experiment was conducted under the same conditions and four samples were filled in four reactor contained in one shell. The results were shown in Table 6.41 and Figs. 6.56-6.58. 

Tests on the activity of LP-produced Fe-based nanopowders for liquefaction of a sub-bituminous coal under high (688 K, 1 h of reaction) and low (658 K, 0.25 h of reaction) severity conditions have been reported.38 The catalysts tested were Fe7C3 (92 m2 g 1 (BET), particle size = 17 nm (XRD))and Fe XS (42 m2 g 1 (BET), particle size = 14 nm (XRD).38 For comparison, a commercial superfine iron oxide catalyst (SFIO, supplied by Mach I, Inc.) whose major phase has been identified in one study as y-Fe20339 (surface area = 195 m2 g 1 (BET), particle diameter = 3 nm (XRD)) and in other study as the ferrihydrite40 was also evaluated under similar conditions. The coal liquefaction experiments were carried out in 50 cm3 horizontal microautoclave reactors loaded with 3 g of sub bituminous Black Thunder coal and 5 g of tetralin used as hydrogen donor. Catalyst loadings of 0.7% and 1.4% of as-received coal... 

The state of iron ammonia catalysts is dealt with in the following chapters, and x-ray, magnetic, and electric data will be discussed together with adsorption measurements. Information about the catalysts combined with kinetic experiments has led to a fairly good qualitative understanding of ammonia synthesis on iron catalysts, but owing to the extremely complicated nature of the catalyst surface during reaction, a quantitative treatment based on data of catalyst and reactants will not be attained in the near future. 

The iron oxide-based catalysts were prepared by Figure 1. Pathways of dehy-a coprecipitation method. In a typical experiment, drogenation of ethylben-1.4 g of catalyst (0.18-0.30mm) was set in a quartz tube reactor. Ethylbenzene was fed through a vaporizer, and was mixed with CO2. The flow rate was 130 ml/min. The dehydrogenation was conducted at 550 °C under atmospheric pressure. The product was analyzed by GC. ... 

Figure 4 shows that activities of several kinds of iron oxide based catalysts. A Fe/Ca/Al oxides catalyst exhibited the best performance among the catalysts tested. Fe/Ca/Al and Fe/Al oxides catalysts were highly active, whereas Fe/Ca and Ca/Al oxides catalyst were extremely low in activity. The selectivities of Fe/Al oxides and Fe/Ca/Al oxides catalysts were almost the same (97% at 5.25 h), and the main by-products were benzene and toluene. Therefore the addition of an optimum amount of CaO to Fe/Al based catalyst could suppress the deactivation of the catalyst during long term reaction. Further experiment are under achievement to elucidate precisely the role of CaO. 

The iron catalysts used in the temperature programmed adsorption experiments were synthesized using iron nitrate precipitated with a base. In the case of the copper/iron catalysts the base used was Na2C03 and for the iron/potassium catalysts, NaOH was used to precipitate... 

TPSR experiments over iron-and ruthenium-based catalysts... 

Thus, ammonia does not reduce magnetite at an appreciable rate at temperatures below 450°C., and it appeal s that at 450°C. and above, the reduction may be accomplished by decomposition products of ammonia rather than by ammonia itself. This contention is based on the fact that the reduction of fused catalysts with ammonia at 450°C. and 550°C. appeared to be an autocatalytic process that is, the rate of reduction increased with time in the initial part of the experiment. Reduction with hydrogen does not appear to be autocatalytic. It may be postulated that a-iron and nitride formed in the reduction are better catalysts for the ammonia decomposition than iron oxide. 

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