Chinthala Praveen Kumar

Vapour phase ammoxidation of toluene over vanadium oxide supported on Nb2O5-TiO2

Vanadium oxide catalysts with V2O5 loadings ranging 1 to 9% (w/w) supported on 1∶1 wt% Nb2O5–TiO2 mixed oxide have been prepared by the wet impregnation method. The calcined samples were characterized by X-ray diffraction (XRD), pulse oxygen chemisorption and temperature programmed desorption (TPD) of NH3. Dispersion of vanadia was determined by oxygen chemisorption at 643 K in a dynamic method. At low V2O5 loadings, vanadia is found to be present in a highly dispersed state. X-Ray diffraction results also suggest that vanadium oxide exists in a highly dispersed state at lower loadings and in a crystalline V2O5 phase at higher vanadia loadings (5 wt% and above). The dispersion of vanadia was found to decrease with V2O5 loading due to the formation of V2O5 crystallites. The catalytic properties were evaluated for the vapor phase ammoxidation of toluene to benzonitrile and correlated with characterization results.

Characterization and catalytic properties of MoO3–V2O5/Nb2O5 catalysts

Abstract The influence of molybdenum oxide on the dispersion of vanadium oxide supported on niobia was investigated. A series of MoO3–V2O5/Nb2O5 catalysts with varying MoO3 content ranging from 1% to 5% (w/w) with fixed V2O5 content were prepared by impregnation of previously prepared 5 wt% V2O5/Nb2O5 with requisite amounts of ammonium molybdate solution. X-ray diffraction patterns indicate the presence of β-(Nb,V)2O5 phase with the addition of MoO3 up to a loading of 3 wt%. Temperature-programmed reduction (TPR) results suggest that the reducibility is decreasing with MoO3 loading. The results of temperature programmed desorption (TPD) of ammonia suggest that the acidity of the catalysts increased with the addition of MoO3. The catalytic properties of the catalysts in the ammoxidation of 3-picoline were correlated with the characterization data.

Dispersion and reactivity of molybdenum oxide catalysts supported on titania

Abstract A series of MoO 3 catalysts with Mo loadings ranging from 2 to 10 w/w% supported on TiO 2 were prepared and investigated by X-ray diffraction (XRD), temperature programmed reduction (TPR) and oxygen chemisorption measurements. Dispersion of molybdena was determined by the oxygen chemisorption at 623 K and by static method on the samples prereduced at the same temperature. At low Mo loadings, i.e. below 6% Mo, molybdenum oxide was found to present in a highly dispersed amorphous state. TPR profiles of MoO 3 /TiO 2 samples suggest that the reduction of MoO 3 to Mo proceeds in two stages and the reducibility of MoO 3 increases with Mo loading in the catalysts. The catalytic properties were evaluated for the vapor-phase ammoxidation of toluene to benzonitrile and are related to the oxygen chemisorption sites.