Abstract
Platinum gauzes have been studied for the partial oxidation of methane in a high-temperature TAP-2 reactor between 800 and 1100°C. Two different oxidation procedures were used and the oxygen uptake has been measured. Alternating pulse experiments with oxygen and methane with various pulse intervals have revealed mechanistic information about the platinum catalyzed partial oxidation. It has been shown that carbon monoxide and hydrogen can be produced directly from methane and solid oxidized platinum. In the absence of gas phase oxygen, the maximum selectivities to carbon monoxide and hydrogen were 97 and 96%, respectively, at a methane conversion of 25%. At low surface oxygen concentrations, oxygen that is incorporated in the platinum bulk diffuses back to the surface to react with surface carbon to carbon monoxide. In that case the surface lifetimes of carbon monoxide and hydrogen are much shorter than the oxygen diffusion time and no consecutive oxidation reactions occur. The results of this study show that production of synthesis gas with high yields is possible by a direct route.
Highlights
Partial oxidation of methane is an attractive way of producing synthesis gas (1–3)
The partial oxidation of methane to synthesis gas can proceed through two routes: (i) indirectly, by total combustion into water and carbon dioxide and subsequent reforming of methane, and (ii) directly, by partial oxidation into hydrogen and carbon monoxide without going through reforming reactions
The oxygen uptake during the preoxidation of the catalyst was much larger than an adsorbed monolayer for both oxidation procedures (Table 1)
Summary
Partial oxidation of methane is an attractive way of producing synthesis gas (1–3). The partial oxidation of methane to synthesis gas can proceed through two routes: (i) indirectly, by total combustion into water and carbon dioxide and subsequent reforming of methane, and (ii) directly, by partial oxidation into hydrogen and carbon monoxide without going through reforming reactions. It has been shown that, under certain conditions and over certain catalysts, carbon monoxide and hydrogen are primary products of the methane oxidation (4–10) This strongly depends on the availability of oxygen and oxygen–surface bond strengths (9). Mentation of synthesis gas production through this route is that the primary products are more reactive for further oxidation to water and carbon dioxide with active oxygen surface species than the reactant methane (10). This limits the possible yields of synthesis gas production with methane and oxygen both present in the gas phase without going through reforming. The idea is that oxygen supplied from a solid phase is less reactive than oxygen supplied from the gas phase
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