A Perspective on Heterogeneous Catalysts for the Selective Oxidation of Alcohols.

Selective oxidation of higher alcohols using heterogeneous catalysts is an important reaction in the synthesis of fine chemicals with added value. Though the process for primary alcohol oxidation is industrially established, there is still a lack of fundamental understanding considering the complexity of the catalysts and their dynamics under reaction conditions, especially when higher alcohols and liquid-phase reaction media are involved. Additionally, new materials should be developed offering higher activity, selectivity, and stability. This can be achieved by unraveling the structure-performance correlations of these catalysts under reaction conditions. In this regard, researchers are encouraged to develop more advanced characterization techniques to address the complex interplay between the solid surface, the dissolved reactants, and the solvent. In this mini-review, we report some of the most important approaches taken in the field and give a perspective on how to tackle the complex challenges for different approaches in alcohol oxidation while providing insight into the remaining challenges.

Towards Mechanistic Understanding of Liquid-Phase Cinnamyl Alcohol Oxidation with tert-Butyl Hydroperoxide over Noble-Metal-Free LaCo1-x Fex O3 Perovskites.

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.