Effect Of Reduction Conditions Research Articles

Platinum catalysts supported on activated carbons: I. Preparation and characterization

Several Pt catalysts supported on activated carbons (manufactured from olive stones and almond shells) have been prepared with both H 2PtCl 6 · 6H 2O and [Pt(NH 3) 4]Cl 2 as metal precursor and using different methods. Once reduced, the supported catalysts were characterized by H 2 and CO chemisorption as well as X-ray diffraction and transmission electron microscopy. The effect of reduction conditions on metal dispersion has been studied and correlated with the surface properties of the supports. The results show that porosity with sizes ranging from 9 to 11 nm is decisive for obtaining a high Pt dispersion. To increase the dispersion of the catalysts prepared from [Pt(NH 3) 4]Cl 2 a treatment with He prior to reduction of the catalysts in H 2 seems to be essential in order to avoid the formation of an unstable hydride which leads to agglomeration of the Pt particles.

Effects of Reduction Conditions on the Catalytic Activity of Rhodium Supported on TiO2 for the Hydrogenation of Carbon Monoxide:Favorable Metal-Support Interaction

Abstract Catalytic activity of Rh/TiO2 was influenced significantly by reduction conditions, the maximum activity per weight being obtained by reduction at 400°C for 2 h, in spite of limited adsorption abilities against reactant gases. The nature of Rh/TiO2 is sensitively modified to develop the most favorable metal-support interaction.

Effect of preparation variables on enantioselectivity of supported nickel catalysts modified with tartaric acid

Enantioselective hydrogenation of methyl acetoacetate to methyl 3-hydroxybutyrate on various supported nickel catalysts modified with ( R,R)-tartaric acid was studied under mild reaction conditions in order to examine the effects of preparation variables on the enantioselectivity and activity of resulting catalysts. The selectivity of the supported nickel catalysts was strongly dependent on the precipitation conditions. The effect of reduction conditions on the selectivity depended on the kind of support. Even Ni-alumina catalysts, when reduced under relatively mild conditions, had high enantioselectivity although their hydrogenation activity was low. Ni-silica catalysts, precipitated under optimum conditions and reduced at 400–500 °C for 1–3 h, were much more active than the other catalysts with similar, high enantioselectivity. Various extents of the selectivity of supported nickel catalysts were explained in terms of the effect of preparation conditions on the crystallite size distributions of nickel.

Effect of reduction conditions upon metal area in CuOZnO catalyst

Effect of reduction conditions upon metal area in CuOZnO catalyst

The treatment of lateritic nickel ores — a further study of the caron process and other possible improvements. Part I. Effect of reduction conditions

An investigation of the reduction roast and ammonia leach method of treating lateritic nickel ore (Caron process) is reported. The effect of the CO 2/CO and H 2O/H 2 couples, both separately and in combination, upon the extraction of nickel from both serpentinic and limonitic ores has been studied as a function of reduction time and temperature, gas composition and particle size. In Part I leaching was carried out with ammoniacal liquors and the influence of aeration and reduction conditions upon the formation of ferric hydroxide which absorbs nickel from the leach liquor was studied. It was found that effective reduction required a minimum partial pressure of p H 2 or p CO of at least 0.15 atm regardless of the type of ore; Partial pressures of reductant above 0.2 atm did not affect the reduction materially. Both the CO 2/CO and H 2O/H 2 couples could be used for selective reduction, but mixtures of the two were less effective than the reductants on their own. The presence of water vapour in the reducing gas appeared to have a deleterious effect upon nickel extraction. In Part II the effect of different leaching agents is reported.