Sulfate-supported metal oxides iron oxide

Sulfate ion was incorporated on alumina and/or silica-alumina or transition metal oxide (iron oxide or zinc oxide) the catalysts were used in the oligomerization of oct-l-ene. The results showed that these sulfated catalysts had a higher activity and selectivity in the olefin oligomerization process, while the conventional catalysts such as cobalt sulfate or magnesium sulfate supported on alumina or silica-alumina exhibited lower activity in the same process. The oligomers had a sufficiently low degree of branching and were useful as a material for, e.g. phthalic acid plasticizer. 

It is well known that SO anions stimulate corrosion of steel surfaces by preventing an in situ formation of iron oxides, which may impede the diffusion processes involved in the corrosion reactions. These sulfate anions are either formed in the atmosphere by oxidation of SO or by direct reaction with the steel surface in the presence of water to form so-called sulfate nests. The latter transformation may take place at the unprotected metal surface or possibly, at least in principal, after SO2 has permeated the organic film and arrived at the metal support. The diffusion of SO anions through organic coatings seems... 

The formation of Fe2(S04)3 can also be prohibited by the use of other metal oxides. Because molybdenum sulfates are not known, iron-molybdenum mixed oxide absorbents were prepared and tested. Figure 7 shows a H2S absorption curve of P5/2Fel2MolO. The capacity is slightly smaller than observed with iron-molybdenum mixed oxide absorbents supported by silica due to the strong interaction of a part of the active compounds with the phosphate groups. The metal phosphates formed are not active in the absorption of H2S. 

The modem process uses a potassium-sulfate-promoted vanadium(V) oxide catalyst on a silica or kie,selguhr support. The SO2 is obtained either by burning pure sulfur or by roasting sulfide minerals (p. 651) notably iron pyrite, or ores of Cu, Ni and Zn during the production of these metals. On a worldwide basis about 65% of the SO2 comes from the burning of sulfur and some 35% by the roasting of sulfide ores but in some countries (e.g, the UK) over 95% conies from the former. 

The existence of these chemical pathways for the oxidation of minerals during bacterial leaching does not exclude a direct role for bacteria. Both pathways may occur simultaneously, the relative importance of each depending upon the rate constants for the reactions and the concentration of Fe(III) present in solution. Experiments carried out on synthetic iron-free cobalt and nickel sulfides, using carefully washed cells of T. ferrooxidans to ensure the absence of Fe(III), showed consumption of oxygen and the solubilization of the metal as sulfate. Solubilization rates were appreciably increased on the addition of Fe(III). These results present support for the presence of both direct and indirect pathways (116). Recently, attempts have been made to compare the rates of these pathways for the oxidation of pyrite by T. ferrooxidans (74). 

The presence of thallium(0) led to an increase in activity and selectivity of metallic palladium catalysts supported on silica in aldose oxidation reactions. However, silica-supported thallium(0) had no activity by itself (entry 3). ° Similarly, the bimetallic catalyst platinum-thallium/ZSM-5, prepared by impregnation of thallium sulfate and chloroplatinic acid on Zeolite Socony Mobil-5 (ZSM-5), showed greater selectivity in propane aromatisation and almost the same catalytic activity as monometallic thallium/ZSM-5 (entry 4). Similar comparison of vanadium-caesium-copper and vanadium-caesium-copper-thallium catalysts supported on TiOa.SiC demonstrated that addition of thallium improved the catalytic activity in partial oxidation of p-tert-butyltoluene to p-tert-butyl-benzaldehyde (entry The application of solid-supported thallium-based catalysts in different processes includes (a) iron-thallium catalysts in carbon monoxide hydrogenations to form hydrocarbons and alcohols, and catalytic reforming of... 

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