Metal oxides, sulfated supported

Metal oxides, 31 78-79, 89, 102, 123, 157-158, 191, 32 199-121 see also Amorphous metal oxides Sulfate-supported metal oxides specific oxides adsorbed oxygen on, 27 196-198 binary, surface acidity, 27 136-138 catalytic etching, 41 390-396 coordination number, 27 136 electrocatalysts, 40 127-128 Fe3(CO)i2 reaction with, 38 311-314 Lewis acid-treated, 37 169-170 multiply-valent metals, electrocatalytic oxidations, 40 154-157 superacids by, 37 201-204 surface acidity, methods for determining, 27 121... 

The table is arranged according to the catalyst in the order metals, oxides, sulfates and other oxy-anions, and miscellaneous. Within each group the order is that of increasing atomic number of the important element. Mixed catalysts are generally listed according to the most abundant component except for metals on supports, which are listed under metals. A few deviations from this order were made to avoid having to refer to the same paper in two places (and for late additions). 

Acid centers, structure, sulfate-supported metal oxides, 37 192-196 Acidic catalysis, 6 241 montmorillonite, 38 266-268 Acidic dissociation constant, probe molecules, 38 210... 

Acidity, 27 284, 285 catalytic performance, 30 121 crystalline titanium silicates, 41 319-320 estimating, 37 166 heteropoly compounds, 41 139-150 ion exchange and, zeolites, 31 5-6 sulfate-supported metal oxides, 37 186-187 surface, monolayer dispersion, 37 34-35 tin-antimony oxide, 30 114-115, 125-1256 Acids, see also specific compounds adsorption of, on oxide surfaces, 25 243-245... 

Moreover, the efficiency of these catalysts could be modihed by tailoring the nature of the metal oxide support and/or reaction conditions (especially the reaction temperature). In this way, interesting conclusions can be obtained when comparing the isobutane/2-butene alkylation catalyzed on two of the most studied catalysts, that is, beta zeolite and sulfated zirconia, when operating at different reaction temperatures. (Table 13.2). ... 

Figure 13.6 Variation of both the conversion of 2-butene and the selectivity to trimethyl-pentanes (TMP), with the nature of the metal oxide support obtained during the isobutene/ 2-butene alkylation at 32°C over sulfated supported on different metal oxides. (After Ref. 35.)...

This review summarizes the recent works on syntheses of solid superacids and their catalytic action, including Lewis acids and liquid superacids in the solid state, as discussed in Sections Il-IV. Sections VI and VII describe new types of solid superacids we have studied in this decade sulfate-supported metal oxides and tungsten or molybdenum oxide supported on zirconia. Perfluorinated sulfonic acid, based on the acid form of DuPont s Nafion brand ion membrane resin, is also gaining interest as a solid superacid catalyst Nafion-H-catalyzed reactions are reviewed in Section V. 

Solid catalysts can be used at elevated temperatures, though their acidities are much weaker than those of liquid ones. From this point of view, solid superacids based on Lewis acids and liquid superacids discussed in Sections II—1V are not sufficiently stable Nafion-H is also unsatisfactory, its maximum operating temperature being below 200°C. A new type of the sulfate-supported metal oxides is more stable because of preparatory heat treatment at high temperatures, but elimination of the sulfate is sometimes observed during reaction, thus it is hoped to synthesize superacids with the system of metal oxides. Another type of superacid, tungsten or molybdenum oxide supported on zirconia, has been prepared by a new preparation method, and its stability is satisfactory so far. It is hoped that the preparation method will be extensively applied to other metal oxides for new solid superacids. 

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). 

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