Vapor-Phase Oxidation of Benzyl Alcohol Using Manganese Oxide Octahedral Molecular Sieves (OMS-2)

Vapor-phase selective oxidation of benzyl alcohol has been accomplished using cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) catalysts. A conversion of 92% and a selectivity to benzaldehyde of 99% were achieved using OMS-2. The role played by the oxidant in this system was probed by studying the reaction in the absence of oxidant. The natures of framework transformations occurring during the oxidation reaction were fully studied using temperature-programmed techniques, as well as in situ X-ray diffraction under different atmospheres

Evidence of solid-solution reaction upon lithium insertion into cryptomelane K0.25Mn2O4 material

Cryptomelane-type K0.25Mn2O4 material is prepared via a template-free, one-step hydrothermal method. Cryptomelane K0.25Mn2O4 adopts an I 4/m tetragonal structure with a distinct tunnel feature built from MnO6 units. Its structural stability arises from the inherent stability of the MnO6 framework which hosts potassium ions, which in turn permits faster ionic diffusion, making the material attractive for application as a cathode in lithium-ion batteries. Despite this potential use, the phase transitions and structural evolution of cryptomelane during lithiation and delithiation remains unclear. The coexistence of Mn3+ and Mn4+ in the compound during lithiation and delithiation processes induce different levels of Jahn-Teller distortion, further complicating the lattice evolution. In this work, the lattice evolution of the cryptomelane K0.25Mn2O4 during its function as a cathode within a lithium-ion battery is measured in a customized coin-cell using in-situ synchrotron X-ray diffraction. We find that the lithiation-delithiation of cryptomelane cathode proceeds through a solid-solution reaction, associated with variations of the a and c lattice parameters and a reversible strain effect induced by Jahn-Teller distortion ofMn3+. The lattice parameter changes and the strain are quantified in this work, with the results demonstrating that cryptomelane is a relatively good candidate cathode material for lithium-ion battery use

Vapor-Phase Oxidation of Benzyl Alcohol Using Manganese Oxide Octahedral Molecular Sieves (OMS-2)

Vapor-phase selective oxidation of benzyl alcohol has been accomplished using cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) catalysts. A conversion of 92% and a selectivity to benzaldehyde of 99% were achieved using OMS-2. The role played by the oxidant in this system was probed by studying the reaction in the absence of oxidant. The natures of framework transformations occurring during the oxidation reaction were fully studied using temperature-programmed techniques, as well as in situ X-ray diffraction under different atmospheres

Nonthermal Synthesis of Three-Dimensional Metal Oxide Structures under Continuous-Flow Conditions and Their Catalytic Applications

Continuous-flow synthesis of one-dimensional (1D) metal oxide nanostructures and/or their integration into hierarchical structures under nonthermal conditions is still a challenge. In this work, a nonthermal, continuous-flow approach for the preparation of γ-manganese oxide (γ-MnO₂) and cerium oxide (CeO₂) microspheres has been developed. By this technique, γ-MnO₂ materials with surface areas of 240, 98, and 87 m²/g and CeO₂ microspheres with a surface area of 1 m²/g have been fabricated successfully. Characterization of the materials was carried out using powder X-ray diffraction, infrared and inductively coupled plasma optical emission spectrometer (ICP/OES), nitrogen sorption, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The synthesized materials showed good catalytic activity in the oxidation of α-methyl styrene