Binary vanadium-titanium oxide catalysts containing 10, 20, 50, and 75 wt. % of V2O5, and TiO2 (anatase), as well as pure V2O5 and TiO2 were studied in microwave assisted vapor-phase oxidation of 3-picoline by oxygen in the presence of nitrogen and water vapors. Selectivity for nicotinic acid was higher than 90% in a large range of 3-picoline conversions over all samples. CO2, 3-pyridinecarbaldehyde, and 3-cyanopyridine were obtained at much smaller amounts. The highest rate of the reaction calculated per square meter of the catalyst surface was observed over pure vanadium oxide. Decrease in vanadium oxide content in the binary catalysts leads to decrease in the rate of 3-picoline conversion. Titanium oxide (anatase) demonstrated the lowest activity. It needed much more energy to heat up pure titanium oxide than pure vanadium oxide to the reaction temperature.The data obtained under microwave heating were compared to the results obtained over the same catalysts by applying classical conventional energy. Under conventional heating, pure vanadium oxide revealed a very low activity similar to the one of titanium oxide. The rates of the reaction over the binary catalysts were almost identical.The kinetics measurements have shown that the lower ratio of oxygen to 3-picoline concentrations is needed to keep the rate of microwave assisted 3-picoline oxidation at the high level.It can be concluded that the microwave heating effect can be located on the V2O5 catalyst active component. The lattice oxygen in the microwave effective dielectric vanadium oxide becomes more mobile, inducing the rate of 3-picoline oxidation to nicotinic acid. .

Vanadium-titanium oxide system in microwave assisted heterogeneous vapor-phase oxidation of 3-picoline to nicotinic acid

247th National Meeting (2014)

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