The kinetics of the semi-batch oxidative synthesis of aniline under atmospheric pressure using DuPont's NiO/ZrO2 cataloreactant was studied in a microreactor flow set-up equipped with a calibrated online mass spectrometer. It was found that the reaction temperature is a crucial parameter for the selectivity to aniline. At 590 K, exclusively aniline was formed, whereas at higher temperatures the decomposition of benzene into C-1 fragments led to the formation of toluene and benzonitrile. TPO experiments carried out in the same reactor subsequent to isothermal aniline synthesis allowed us to derive the degree of coking and the degree of NiO reduction.