Synthesis, characterization and catalytic performance of titania supported VPO catalysts for the ammoxidation of 3-picoline

Series of vanadium phosphorus oxide (VPO) catalysts supported over titania (anatase) were synthesised with varying contents of VPO (5-50 wt%). These solids were characterised by ICP-OES,TG/DTA, BET, XRD, FTIR (Py-ads) and XPS. The catalytic activity was evaluated for ammoxidation of 3-picoline (3-pic) to nicotinonitrile (NN) in a fixed bed catalytic reactor. Thermal analysis provided good hints on the phase transformation of VHP precursor into active VPP phase at around 400 degrees C. BET surface areas and pore volumes are found to depend on VPO loading and varied in the range from 70 m(2)/g to 133 m(2)/g. XRD demonstrates the formation of (VO)(2)P2O7 (VPP) phase. XPS showed that an average oxidation state of vanadium around 4.0, which is found to be unaltered in the spent samples. FTIR (Py-ads) revealed the presence of both Lewis and Bronsted sites with varying proportions, which again depend upon VPO loading. Correlation of acidic properties (Lewis and Bronsted acid sites) of the catalysts with that of performance of catalysts was explored. VPO loading has a clear influence on the acidic properties and thereby catalytic activity and selectivity. Catalytic results showed that the supported catalysts gave better performance compared to bulk VPO. Yield of NN increased up to 20 wt% VPO loading and then decreased with further increase in VPO content. Among all catalysts tested, the 20 wt%VPO/TiO2 exhibited the best performance (X-3-pic = ca. 100% and Y-NN = 83%). (C) 2010 Elsevier B.V. All rights reserved.