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No description available.

No description available.

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Rhodium, platinum, copper, palladium, and rhodium-ceria catalysts were investigated in the catalytic partial oxidation of methyl acetate, the simplest methyl ester, to better understand the conversion of biodiesel to hydrogen. Only rhodium and rhodium-ceria catalysts allowed for an autothermal reactor operation. Both catalysts were active in producing hydrogen, carbon monoxide, water, and carbon dioxide, although the rhodium-ceria catalyst showed the greater methyl acetate conversion and the greater hydrogen and carbon monoxide selectivities. A low C/O feed ratio favored the methyl acetate conversion, the hydrogen selectivity, and the carbon monoxide selectivity. Furthermore, a high gas hourly space velocity also improved the reactor performance. According to the experimental data, it appears that the oxidation of methyl acetate forms carbon monoxide and water as a primary step, instead of carbon dioxide and water as with the combustion reaction. In general, methyl acetate does not yield more synthesis gas than biodiesel. The methyl ester functional group limits the hydrogen yield and hence new catalysts should be developed and investigated in order to better target the decomposition of methyl esters to hydrogen.

Alkane-rich fractions including n-paraffins are the most important chemical feedstock used in the / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2008.

Alkaline pressure oxidation, particularly in the presence of trona as additive, can be used to oxidize high carbonate refractory gold ores as it prevents the formation of CO2 in the autoclave. However, the presence of silica in the ore can lead to the encapsulation of pyrite due to the formation of a passive layer. This phenomenon occurs due to the high solubility of silica in alkaline solutions and its subsequent re-precipitation on the reacting pyrite surface. The present study investigated the chemical composition and thickness of the passive layer on a rotating pyrite surface in an aqueous slurry containing silica sand, sodium carbonate and calcium carbonate at 230°C and under 7 bar of oxygen overpressure. Results obtained from XPS and SEM show that a concentration of 2.5 g/L sodium carbonate gave the maximum thickness of passivation on pyrite and that the passive layer consisted primarily of silicates and aluminosilicates.

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No description available.