Pelargonium zonale as a Source of Active Catalysts for the Oxidation of Geraniol with Oxygen

The sustainable utilization of post-consumer plant biomass as a precursor for functional carbon materials has attracted increasing attention as an environmentally friendly approach to heterogeneous catalyst development. In this study, the aerial parts of Pelargonium zonale were converted into activated carbons by chemical activation with KOH at carbonization temperatures of 750, 800, and 850 °C. The obtained materials were comprehensively characterized using N₂ adsorption-desorption, XRD, FTIR, UV-Vis spectroscopy, XRF, and SEM. Increasing the carbonization temperature promoted pore development, resulting in activated carbons with a maximum specific surface area of 1578 m² g^-1 and a total pore volume of 0.751 cm³ g^-1. The catalytic performance of the obtained materials was evaluated in the oxidation of geraniol. No direct correlation between the textural properties of the activated carbons and their catalytic performance was observed, suggesting that catalytic behaviour results from the combined effect of several physicochemical properties. Optimization of the reaction conditions demonstrated that catalytic performance depended on the combined influence of reaction temperature, catalyst amount, reaction time, and catalyst properties. Under the optimized reaction conditions (110 °C, 0.5 wt% catalyst, and 360 min), the highest geraniol conversion (37 mol%) was achieved over CP_KOH_850. Kinetic modelling confirmed that geraniol oxidation proceeds through a complex network of parallel and consecutive reactions leading to the formation of citral, 2,3-epoxygeraniol, 2,3-epoxycitral, and other oxidation products. These findings demonstrate that waste Pelargonium zonale biomass is a promising renewable precursor for the preparation of functional carbon materials for heterogeneous catalytic applications.