OXIDATION OF ETHANE OVER SILICA-SUPPORTED ALKALI-METAL VANADATE CATALYSTS

The partial oxidation of ethane has been investigated on silica-supported alkali metal vanadate catalysts in a fixed-bed continuous-flow reactor at 770-823 K using N2O as oxidant. Pulse experiments, temperature-programmed reduction of the catalyst, and catalytic decomposition of N2O and C2H5OH were also carried out. The main products of the oxidation reaction were ethylene, acetaldehyde, CO, and CO2 Small amounts of CH4, C2H5OH, C3-, and C4-hydrocarbons were also identified. The introduction of water increased the acetaldehyde selectivity but decreased that of ethylene. In the presence of water the acetaldehyde selectivity increased from LiVO3 to RbVO3. Detailed kinetic measurements were carried out on KVO3/SiO2. From the pulse experiments it was inferred that in the oxidation of ethane an intermediate more reactive than C2H6 is formed for the activation of the catalysts. The temperature-programmed reduction spectra of alkali vanadates show that the onset temperature of the main reduction stage increased, while the extent of the reduction decreased somewhat from Li to Cs. A possible mechanism for the oxidation reaction is discussed. © 1991.