| Abstract |
Carbon supported transition metals such as Cu, Co, Ni and Fe are proved to be active catalysts for selective NOx reduction in an oxygen-free atmosphere. In this work, metal-free carbon xerogels (CX) obtained by sol-gel polymerization of resorcinol and formaldehyde together with Cu, Co and Fe-doped and impregnated CX were studied in the reduction of NOx in the absence and presence of an external reductant (H-2). Moreover, the influence of the surfactants (CTAB, Pluronic P123, Span 80) and the type of metal used as dopant on the morphology and textural properties of carbon xerogels was investigated. Moderately high surface areas were obtained (420-700m(2) g(-1)). N-2 adsorption and SEM images revealed that the pore structure and morphology of the gel were strongly affected by the type of surfactant: the most developed porous structure was obtained by using Span 80, while the worst by Pluronic P123. Furthermore, better-defined carbon microspheres were obtained in metal-doped samples when compared to the metal-free carbon xerogel, especially for Fe-doped CX in which perfectly spherical and isolated particles were observed. However, impregnated catalysts exhibit higher NO conversion when compared to the doped ones. Cu/CX presents the best catalytic activity among all the samples with total NO conversion into N-2 at 200 degrees C in the presence of H-2. In addition, TGA analysis revealed that this catalyst has a higher thermal stability in air in comparison to CX being completely stable up to 420 degrees C, thus, Cu/CX is presented as optimal candidate for NOx reduction in both reductant and oxidant atmospheres with better catalytic performance than Cu/zeolites systems |
