Towards Mechanistic Understanding of Liquid‐Phase Cinnamyl Alcohol Oxidation with tert‐Butyl Hydroperoxide over Noble‐Metal‐Free LaCo1–xFexO3 Perovskites. Issue 8 (23rd August 2019) - Waffel, Daniel
Abstract: Noble‐metal‐free perovskite oxides are promising and well‐known catalysts for high‐temperature gas‐phase oxidation reactions, but their application in selective oxidation reactions in the liquid phase has rarely been studied. We report the liquid‐phase oxidation of cinnamyl alcohol over spray‐flame synthesized LaCo1– x Fex O3 perovskite nanoparticles with tert‐ butyl hydroperoxide (TBHP) as the oxidizing agent under mild reaction conditions. The catalysts were characterized by XRD, BET, EDS and elemental analysis. LaCo0.8 Fe0.2 O3 showed the best catalytic properties indicating a synergistic effect between cobalt and iron. The catalysts were found to be stable against metal leaching as proven by hot filtration, and the observed slight deactivation is presumably due to segregation as determined by EDS. Kinetic studies revealed an apparent activation energy of 63.6 kJ mol −1 . Combining kinetic findings with TBHP decomposition as well as control experiments revealed a complex reaction network. Abstract : Versatility of perovskites : LaCo1– x Fe x O3 perovskites were found to be active and selective for the liquid‐phase oxidation of cinnamyl alcohol to cinnamaldehyde with tert ‐butyl hydroperoxide, leading to conversions of up to 89 %. A complex reaction network leading to benzaldehyde via cinnamaldehyde epoxide was identified. The peroxide decomposition is the rate‐determining step initially, while the reaction of the organic substrates with the formed organic radicals is rate‐determining after 10 min.