Iron sponge catalyst

Still following the macro-structural hypothesis which we favored at that time, we abondoned the idea of a specific favorable influence of flux promoters and assumed instead that the cause for the success of the magnetite experiment was the compact porous structure of the iron sponge which was formed in the test oven by the reduction of the Swedish ore. An apparent support of this idea was that contrary to the favorable action of the dense iron sponge obtained from magnetite, catalysts of a looser structure such as, e.g., iron asbestos preparations had always been particularly ineffective. 

Following the development of sponge-metal nickel catalysts by alkali leaching of Ni-Al alloys by Raney, other alloy systems were considered. These include iron [4], cobalt [5], copper [6], platinum [7], ruthenium [8], and palladium [9]. Small amounts of a third metal such as chromium [10], molybdenum [11], or zinc [12] have been added to the binary alloy to promote catalyst activity. The two most common skeletal metal catalysts currently in use are nickel and copper in unpromoted or promoted forms. Skeletal copper is less active and more selective than skeletal nickel in hydrogenation reactions. It also finds use in the selective hydrolysis of nitriles [13]. This chapter is therefore mainly concerned with the preparation, properties and applications of promoted and unpromoted skeletal nickel and skeletal copper catalysts which are produced by the selective leaching of aluminum from binary or ternary alloys. 

In the majority of cases, the last step in the preparation of catalytically active metals is a reduction. The precursor is very frequently an oxide. An oxychloride is the real precursor of active platinum and some noble metals if chlorometal complexes (e.g. chloroplatinic acid) are used. It may be advantageous to use still other precursors and to reduce them directly without any intermediary transformation to oxide. On the other hand, nearly all catalytic metals are used as supported catalysts. The only notable exception is iron for ammonia synthesis, which is a very special case and then the huge body of industrial experience renders scientific analysis of little relevance. The other important metals are Raney nickel, platinum sponge or platinum black, and similar catalysts, but they are obtained by processes other than reduction. This shows the importance of understanding the mechanisms involved in activation by reduction. 

In the case of high-temperature, fluidized-bed reactors operation at higher pressures has an additional benefit in that the rate of carbon deposition on iron catalysts is proportional to Pgg/P H2 (ref. 2). As the partial pressures increase, the carbon deposition rate decreases. Because the deposited carbon has a high area and acts like a sponge for retaining wax, the rate of wax accumulation on the catalyst also decreases with increasing pressure (ref. 2). The benefit of this is that the catalyst particles are less likely to become "sticky" and result in defluidization of the bed. The CFB reactors at Sasol Two and Three operate at higher pressures than the older units at Sasol One, and the lower deposition rates of carbon and wax on... 

The key to the extremely high activity for filament production found with FeO may well reside in the defect structure of this compound. In such a structure the oxygen atoms in the surface will be readily accessible to extraction by protons generated by the hydrocarbon decomposition reaction and as a result the oxide could rapidly attain at the surface an iron rich sponge-like arrangement i.e. the role of FeO is that of a precursor for a high surface area Fe catalyst formed ln-sltu. 

Alcan 756 C.l. 77775 Carbonyl nickel powder CCRIS 427 EINECS 231-111-4 EL12 Fibrex Fibrex P HSDB 1096 Ni 0901-S Ni 270 Ni 4303T Nichel Nickel 200 Nickel 201 Nickel 205 Nickel 207 Nickel 270 Nickel catalyst Nickel compounds Nickel, elemental Nickel, elemental/metal Nickel particles Nickel sponge NP 2 Raney alloy Raney nickel RCH 55/5. Metallic element, used in electroplating, as a hydrogenation catalyst and in iron- and copper-based alloys. Metal mp = 1453° bp (calc) = 2732° d= 8.908. Atomergic Chemetals Inco, Europe Lancaster Synthesis Co. Sigma-Aldrich Fine Chem. 

The addition of an iron catalyst to the treated solution allows the formation of OH via Fenton s reaction (1). In 1986, M. Sudoh et al. were the first to apply the method to wastewater treatment. Since then, graphite, carbon-PTFE O2 diffusion, carbon felt, activated carbon fiber (ACF), reticulated vitreous carbon (RVC), carbon sponge, and carbon nanotubes (CNTs) have been used as cathode materials [1]. 

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