Nano-confined manganese oxide on SBA-15 for ethylene catalytic oxidation

Abstract

This study investigates the synthesis and catalytic performance of nano-confined manganese oxide (MnO_x) on SBA-15 for ethylene oxidation. A “med-synthesis” approach, involving dry impregnation of manganese nitrate on as-synthesized SBA-15 via grinding, was employed to achieve high MnO_x loading and controlled dispersion within the mesoporous channels. The resulting catalysts (xMn/SBA-15_d) were characterized by XRD, SAXS, TEM, TGA, and XPS to understand the impact of MnO_x content on structural properties and catalytic activity. The results demonstrate that the dry impregnation method leads to well-dispersed MnO_x nanoparticles within the SBA-15 framework, even at high loadings (up to 30 wt%). In contrast, wet impregnation resulted in larger MnO_x particles and a loss of the ordered mesoporous structure. The nano-confined MnO_x particles exhibited excellent thermal stability, resisting sintering even after prolonged exposure to high temperatures (550 °C) under reaction conditions. Catalytic testing revealed that the 20 wt% Mn loaded on SBA-15 via the med-synthesis approach displayed superior activity for ethylene oxidation compared to the wet-impregnated counterpart, achieving complete conversion at lower temperatures. In situ TEM studies further confirmed the stability of the nano-confined MnO_x particles, highlighting the potential of this med-synthesis approach for developing highly active and durable catalysts for volatile organic compound oxidation.