000K utf8 1100 2021$c2021-01-27 1500 eng 2050 urn:nbn:de:hbz:464-20210127-144420-9 2051 10.1021/acscatal.9b01048 3000 Anke, Sven 3010 Antoni, Hendrik 3010 Bendt, Georg 3010 Hajiyani, Hamidreza 3010 Jeon, Hyosang 3010 Muhler, Martin 3010 Pentcheva, Rossitza 3010 Roldan Cuenya, Beatriz 3010 Schulz, Stephan 3010 Sinev, Ilya 3010 Zegkinoglou, Ioannis 4000 Selective 2-Propanol Oxidation over Unsupported Co3O4 Spinel Nanoparticles$dMechanistic Insights into Aerobic Oxidation of Alcohols [Anke, Sven] 4209 Crystalline Co3O4 nanoparticles with a uniform size of 9 nm as shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM) were synthesized by thermal decomposition of cobalt acetylacetonate in oleylamine and applied in the oxidation of 2-propanol after calcination. The catalytic properties were derived under continuous flow conditions as a function of temperature up to 573 K in a fixed-bed reactor at atmospheric pressure. Temperature-programmed oxidation, desorption (TPD), surface reaction (TPSR), and 2-propanol decomposition experiments were performed to study the interaction of 2-propanol and O2 with the exposed spinel surfaces. Co3O4 selectively catalyzes the oxidative dehydrogenation of 2-propanol, yielding acetone and H2O and only to a minor extent the total oxidation to CO2 and H2O at higher temperatures. The high catalytic activity of Co3O4 reaching nearly full conversion with 100% selectivity to acetone at 430 K is attributed to the high amount of active Co3+ species at the catalyst surface as well as surface-bound reactive oxygen species observed in the O2 TPD, 2-propanol TPD, TPSR, and 2-propanol decomposition experiments. Density functional theory calculations with a Hubbard U term support the identification of the 5-fold-coordinated octahedral surface Co5c3+ as the active site, and oxidative dehydrogenation involving adsorbed atomic oxygen was found to be the energetically most favored pathway. The consumption of surface oxygen and reduction of Co3+ to Co2+ during 2-propanol oxidation derived from X-ray absorption spectroscopy and X-ray photoelectron spectroscopy measurements before and after reaction and poisoning by strongly bound carbonaceous species result in the loss of the low-temperature activity, while the high-temperature reaction pathway remained unaffected. 4950 https://doi.org/10.1021/acscatal.9b01048$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:hbz:464-20210127-144420-9$xR$3Volltext$534 4961 https://duepublico2.uni-due.de/receive/duepublico_mods_00073934 5051 530 5051 540 5550 2-propanol 5550 Co3O4 5550 DFT+U 5550 selective oxidation 5550 surface spectroscopy