This experiment aimed to preliminarily explore the effect of different operating conditions (liquid feed flowrate, pressure, and temperature) on the reaction outcome, and to investigate the catalyst stability. The gas flowrate was kept constant, while different temperatures, pressures and liquid flowrates were selected within the operating conditions intervals reported in Table , in such a way to ensure liquid phase conditions. The results of the optimization test are presented in Figure . The experiment was initially carried out at 30 bar and 200 °C, feeding 0.3 mL/min of liquid feed solution. Co3O4 proved to be catalytically active and selective in the oxidation of 2-butanol to MEK, with 6% conversion and 5% selectivity. Only 2butanol and MEK were detected in the liquid-phase samples, while, in the gas phase, the only detected byproduct was CO2, presumably generated by further oxidation of MEK. After four days of operation in the same conditions, the liquid feed flowrate was lowered down to 0.1 mL/min, leading to an increase of both the conversion (10%) and the yield (6%) as a result of the increase of the permanence time of the reacting mixture in the reactor. Then, the operating pressure was increased to 40 bar. This had the effect of increasing the oxygen concentration, and the conversion and yield increased even further (13% and 8%, respectively).