Nickel ferrite samples of different crystallite sizes with the nominal composition NiFe2O4 were prepared and found to largely differ not only in expectable properties such as the specific surface area, but also in reducibility towards hydrogen and carbon monoxide, desorption characteristics, share of ions Ni 2+ and Fe 3+ ions in octahedrally and tetrahedrally coordinated sites and reactivity and selectivity in the oxidative dehydrogenation of 2-propanol, which was studied at two different 2-propanol:O2 ratios. While the sample of high crystallinity prefers the non-oxidative dehydrogenation pathway, the sample of low crystallinity tends to unselectively catalyse not only the selective oxidation of 2-propanol, but also total combustion and partial oxidation of 2-propanol. The latter trend is amplified at an increased O2 level. Ex-situ XRD measurements of the used catalysts showed, that the low crystallinity sample is subject to partial reduction and formation of a face centred cubic metal phase and carbon deposition in various reactions represented by equations ( ) -( ) more readily than the higher crystallinity sample, which agrees with results gained in H2-and CO-TPR experiments. In the operando-DRIFTS-MS experiments, 2-propoxide and adsorbed acetone were found to be essential intermediates in the selective oxidation of acetone and the samples found to form acetates carbonates differently interacting with co-or preadsorbed O-H groups. Closure of carbon balance appeared to be poor most likely due to the formation of adsorbates, which was estimated semiquantitatively using results from the IR studies. Higher selectivity towards total combustion and partial oxidation of 2-propanol in the lower crystallinity sample is linked to a larger gap in the carbon balance, especially at the higher O2 level, compared to the higher crystallinity sample. These results show, that the spinel structure developed more properly in the higher crystallinity sample correlates with a higher selectivity for the oxidation of 2-propanol to acetone.