Abstract
Mechanism of the oxygen involvement in nicotinic acid formation under β-picoline oxidation on vanadia-titania catalyst was studied by in situ FTIR spectroscopy and kinetic method in temperature range of 120–300 °C. The formation of nicotinic acid proceeds via a consecutive transformation of the surface carbonil-like and carboxylate complexes stabilized at reduced vanadium. Catalyst oxygen includes in formation of these complexes. Carboxylate is a direct precursor of nicotinic acid, it turns into nicotinic acid in the presence of the gas-phase oxygen in joint step of catalyst reoxidation–acid desorption. Significant concentration ratio of oxygen to β-picoline (C O2:C βP > 16:1) is necessary to effective running reaction. This factor can be explained by the reaction mechanism. The variety of oxygen functions and of oxygen species require the maximum oxidized state of the catalyst and explain the necessity of a high oxygen excess in the reaction mixture.
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