engleski

Catalytic oxidation of toluene on hydrothermally prepared ceria nanocrystals

Ceria, CeO2, owing to high mobility and oxygen storage capacity within the lattice, has been one of the most widely used heterogeneous catalysts. Due to its superior properties recent research has been focused on the nanoscale ceria. Different synthesis approaches have been used for synthesis of ceria nanocrystals, among which hydrothermal process possesses numerous advantages such as simplicity, affordability and environmentally benignity. Therefore, nanocrystalline ceria was prepared by means of hydrothermal process using Ce(SO4)2×3H2O and NaOH as precursors. The obtained product has been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 gas adsorption–desorption isotherms and diffuse reflectance UV–Vis spectroscopy (DRS). The catalytic performances of the prepared catalyst have been evaluated for toluene oxidation in the fixed bed reactor. The influence of different reaction conditions on the catalytic performance was examined using gaseous mixture of toluene and nitrogen (242 ppm of toluene/nitrogen) using air as an oxidant. Catalytic measurements were performed at different temperatures (100-450°C) and various total flow rates of the reaction mixture (23-138 cm3 min-1) at the constant catalyst mass (0.05 g). Pure ceria with crystallite size of 4 nm, determined by Scherrer method from XRD pattern, and the approximately same particle size according to TEM micrograph has been obtained. Specific surface area of prepared nanoparticles determined using BET analysis of nitrogen adsorption-desorption isotherms yields 201 m2g- 1, while bandgap of 3.2 eV has been estimated from DRS spectrum via Tauc‘s plot. Catalytic tests showed good activities for the toluene oxidation with T50 temperatures, corresponding to 50% of the toluene conversion, observed at 250°C and even lower temperatures depending on total flow rate of the gas mixture. The appropriate mathematical one-dimensional (1D) pseudo-homogeneous model of the fixed bed reactor was proposed to describe the reactor performance. Proposed model was validated by comparing experimental data and model predictions. The obtained results could be fundamental for designing ceria-based catalysts with good performances for catalytic oxidation of different volatile organic compounds.

ceria ; catalytic oxidation ; nanomaterials ; toluene ; modeling

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