Abstract
Heterogeneous catalytic vapor-phase oxidation of methylpyridines is "green", the most simple and perspective method for obtaining pyridinecarboxylic acids. Vanadium-titanium catalysts have a wide application in some important industrial processes of oxidation. Oxidation of 3-and 4-methylpyridine on vanadium-titanium catalysts has been investigated and for its preparation various titanium crystal modifications were used. Characterization of the catalysts was carried out by using the X-ray diffraction, N2-adsorbtion and thermal dissociation of V2O5. It was found that the use of anatase type of TiO2 with a higher BET surface area enhances the activity of the vanadium-titanium catalyst extremely. XRD-characterization of catalysts demonstrated that the only V2O5 and anatase or V2O5 and rutile phase was detected. It was established that the use of titanium dioxide of crystal modifications of anatase increases on the order of the dissociation rate V2O5. It was shown that vanadium-titanium catalysts' activity and selectivity in investigated processes depends on TiO2 crystal modifications.V2O5-anatase is more active and selective in formation of pyridine carboxylic acids. V2O5-rutile in the process of oxidation of 4-methylpyridine on the catalyst forms the mixture of isonicotinic acid and its aldehyde. Connection between the dissociation rate of V2O5 in catalysts of V2O5-anatase and V2O5-rutile and their activity in isomeric methylpyridines oxidation was established. High surface area, anatase structure of titanium are the key parameters determining the activity and selectivity of vanadium-titanium oxidation catalysts.