Global kinetic model: a case study on the N-oxidation of alkylpyridines.

The homogeneous catalytic N-oxidation of two picolines and two lutidines by hydrogen peroxide has been studied calorimetrically using a heat flow and power compensation SIMULAR reaction calorimeter. The objective of this work was to extend a previously developed kinetic model [J. Sempere, R. Nomen, J.L. Rodriguez, M. Papadaki, Modelling of the reaction of 2-methylpyridine using hydrogen peroxide and a complex metal catalyst, Chem. Eng. Process. 37 (1998) 33-46] for 2-methylpyridine to more reactions in the same family. The kinetic model is in good agreement with our experimental data on beta-picoline. 3,5-Lutidine is in adequately good agreement with the model. However, the formation of two phases during the course of the reaction imposes the need for modifications to allow for mass transfer considerations. The N-oxidation of 2,6-lutidine is controlled by the addition or availability of hydrogen peroxide. A different reactor design is necessary for operation at the kinetic regime. High temperatures and catalyst concentrations enhance the selectivity towards N-oxidation of all alkylpyridines studied. The power evolution of all reactions has similar profiles thus indicating that similar kinetics are followed. The study of the N-oxidation of this family of compounds indicates that it is possible to design a process where hydrogen peroxide decomposition can be practically totally suppressed.