Novel cryptomelane nanosheets for the superior catalytic combustion of oxygenated volatile organic compounds.

This work offers a novel pathway to prepare cryptomelane manganese oxides nanosheets as an superior catalyst for the catalytic combustion of oxygenated volatile organic compounds. The tunnel cryptomelane manganese oxides nanosheets were prepared from layered birnessite via simultaneously tuning pH and molar ratio (ROK) of the redox-precipitation between oxalic acid and KMnO4. Thus, few-layered cryptomelane nanosheets possessing the most predominantly exposed (211) facet are generated at low pH (5.2-5.6), which intensifies the surface area of thin crystal cryptomelane nanosheets up to 177 m2g-1 and weakens Mn-O bonds. Moreover, high ROK results in low manganese average oxidation state (AOS), greater oxygen vacancies and better low-temperature reduction and oxygen mobility. Such features significantly maneuver the catalytic activity of the cryptomelane nanosheets catalysts for the complete oxidation of oxygenated volatile organic compound (e.g., 2-propanol, acetone) at low temperature (170-230 °C). Moreover, the catalysts show high stability for 48 h. The presented catalyst discloses an avenue to address current obstacles in the catalytic oxidation of volatile organic compounds.

Synthesis of Diatomite-Based Mesoporous Wool-Ball-Like Microspheres and Their Application for Toluene Total Oxidation Reaction.

Diatomite (DE) has attracted considerable attention owing to its abundance, low cost, and potential for a wide variety of applications. This work reports the development of mesoporous wool-ball-like (WBL) microspheres from natural DE through a simple hydrothermal treatment. We discovered that the presence of cetyltrimethylammonium bromide is a prerequisite for generating monodispersed WBL microspheres. The mechanism for the transformation of pristine DE into mesoporous microspheres through dissolution-recrystallization was clearly investigated. Interestingly, the microspheres exhibited a specific surface area 25-60 times larger than that of the pristine DE. The application of WBL microsphere DE as an effective support for metallic catalysts in the toluene total oxidation reaction was demonstrated.