Catalytic Abatement of Volatile Organic Compounds and Soot over Manganese Oxide Catalysts.

A set of manganese oxide catalysts was synthesized via two preparation techniques: solution combustion synthesis (MnO/MnO-SCS and MnO-SCS) and sol-gel synthesis (MnO-SG550 and MnO-SG650). The physicochemical properties of the catalysts were studied by means of N-physisorption at -196 °C, X-ray powder diffraction, H temperature-programmed reduction (H-TPR), soot-TPR, X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FESEM). The high catalytic performance of the catalysts was verified in the oxidation of Volatile Organic Compounds (VOC) probe molecules (ethene and propene) and carbon soot in a temperature-programmed oxidation setup. The best catalytic performances in soot abatement were observed for the MnO-SG550 and the MnO/MnO-SCS catalysts. The catalytic activity in VOC total oxidation was effectively correlated to the enhanced low-temperature reducibility of the catalysts and the abundant surface O-species. Likewise, low-temperature oxidation of soot in tight contact occurred over the MnO-SG550 catalyst and was attributed to high amounts of surface O-species and better surface reducibility. For the soot oxidation in loose contact, the improved catalytic performance of the MnO/MnO-SCS catalyst was attributed to the beneficial effects of both the morphological structure that-like a filter-enhanced the capture of soot particles and to a probable high amount of surface acid-sites, which is characteristic of MnO catalysts.