TiO2–SiO2 mixed oxide supported MoO3 catalyst: Physicochemical characterization and activities in nitration of phenol

12 wt% MoO3/TiO2–SiO2 solid acid catalyst was prepared and calcined at various temperatures. The calcined catalyst was characterized by XRD, FT-IR, BET, SEM, NH3-TPD and pyridine adsorbed FT-IR methods. The effect of calcination temperature on activity of catalyst was studied by choosing liquid phase nitration of phenol as a model reaction. For the same reaction effect of various solvents, effect of reaction time and reusability of the catalyst was also studied. Catalyst calcined at 500 °C temperature showed highest phenol conversion whereas greater o-nitrophenol selectivity is claimed over catalyst calcined at 700 °C. It was observed that high phenol conversion co-relates with the presence of greater number of strong Brönsted acid sites over the catalyst surface whereas the selectivity of o-nitrophenol is related to the pore size of the catalysts. No use of sulfuric acid along with the nitric acid used in its diluted form in the reaction makes the process safe and environmentally friendly.

Reaction proceeds via formation of nitronium ions over the Brönsted acid sites of the catalyst and later attack of those at ortho- and para-position of phenol.Figure optionsDownload high-quality image (61 K)Download as PowerPoint slide