An environmental scanning electron microscope (ESEM) was used to study the gasification of an activated carbon catalyzed by MoO3 in air and oxygen atmospheres and by a eutectic mixture and alloy of MoO3 and V2O5. In an air atmosphere, the melting of MoO3 starts at 630°C and the reaction occurs by preferential gasification on the edges of carbon particles. In an O2 atmosphere, however, homogeneous gasification is observed in all directions. This difference can be explained by more extensive oxidation of the carbon surface in an oxygen atmosphere and the more effective spreading of the catalysts on charcoal surfaces. The ESEM experiments showed that some particles of the eutectic alloy of MoO3 and V2O5 had higher melting points than those of the single oxides. The analysis of alloy particles by EDS and by electron microprobe indicated that large areas of single oxides are segregated and encapsulated by the other oxide in some alloy particles. It is proposed that the encapsulation of either oxide (MoO3 or V2O5) inhibits the initial contact of the catalyst with the carbon surface and leads to different reactions than those which take place on carbon surfaces. A lower activity of the "eutectic" alloy, compared to that of the binary mixture with the eutectic composition, is, thus, ascribed to the heterogeneous composition of alloy particles which can give rise to the formation of different oxide phases with higher melting points than those of the single oxides.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology