Interestingly, the formation of hydrogen is also detected at higher temperatures. During cooling, the local maximum in the acetone formation was not observed. A second cycle was performed to assess the stability of the catalyst after the first cycle. The overall trend of the profiles appears to be similar, but on closer inspection the local maximum at 195 °C is not present, and the onset of the reaction is shifted to higher temperatures. The plateau is shorter, although the maximum conversion is similar. The same test was performed on MnCo2O4. In this case, the activity onset is 70 °C, much like for Co3O4, and the CO2 formation starts at 235 °C, but the local maximum is absent. The profiles generally follow the same trend. While MnCo2O4 was the most active catalyst in the liquid phase, its activity in the gas phase is lower. During the second cycle the maximum conversion is considerably lower. For both solids, the spinel phase is converted into rock-salt, monoxide structures, indicating that the catalysts are reduced by the process (Figure ).