Physical Adsorption Studies on Mixed Vanadium Oxide Catalysts

Abstract

Physisorption of N 2 gas at 77 K has been used to measure the surface area (S BET ) and porosity of V 2 O 5 pure and mixtures with Fe, Co or Ni ions in atomic ratios extending from 1 to 50 at %. Calcination of samples was carried out between 473 and 873 K in flowing air. Adsorption isotherms are of type IV in the Braunauer classification with hysteresis loops of mixed A and B types, which reveal a very small external surface. Calculation of the pore volume distribution was carried out in addition to V a -t plots in order to study the surface porosity nature which was found to be mesoporous. Finally, the effect of foreign ions on S BET was discussed.