Enhanced γ-phase crystallinity of Al2O3 frameworks at the concave surface of PS-b-PEO templated spherical pores

Utilization of Reactive Nitrogen Compounds for Nitrogen Circular Economy

Nitrogen oxides (NOx) should be purified according to environmental regulations, being restricted increasingly year by year. A wide variety of denitration technologies, such as selective catalytic reduction (SCR) of NOx to nitrogen (N2) and NOx storage reduction (NSR) to N2 by injecting reducing agents like ammonia (NH3), has so far been developed practically. Sophisticated catalytic approaches are perhaps mandatory for the sustainability in energy including complete purification of NOx. As one of the solutions to overcome problems for environment and resource simultaneously, this concept article focuses on the utilization of reactive nitrogen (Nr) compounds, mainly NOx, for encouraging an opening to consider nitrogen circular economy. For the recycling of NOx via NH3, a challenging but rational catalytic technology can be proposed by an alternate switching the inlet gas between NOx containing oxidative gas and H2 containing reductive one without an operation to change the reaction temperature. Considering the reactivity of NOx higher than that of N2, this kind of NOx to NH3 (NTA) process is promising for synthesizing NH3, being valuable not only as fertilizer but also as fuel in near future.

Smart synthesis of highly porous metal oxide powders with the self-assembly of amphiphilic organic compounds

Supramolecular chemistry-mediated synthesis has thus far been employed for the design of ordered mesoporous structures surrounded by various metal oxides that are helpful as nanometer-scaled unique reaction containers with high specific surface area, large pore volume and uniform mesopores useful for the storage and mass transport of large-sized molecules. The evaporation-induced self-assembly (EISA) process is very powerful for fabricating mesoporous metal oxide films with the rapid evaporation of solvents. Although a similar EISA process is also applied to synthesize mesoporous metal oxide powders using the room-temperature drying process with slow evaporation of solvents, the control of the evaporation rate should be quantified for the complete reproduction of high-quality metal oxide powders. In this feature article, I introduce our recent challenge in synthesizing highly porous metal oxides in powder form with the smart optimization of synthetic conditions by combining several EISA processes to eliminate the mismatch of the rate of solvent evaporation, inducing the self-assembly of amphiphilic organic molecules.

Efficient optimization of the synthetic conditions for aerosol-assisted high-quality mesoporous CeO2 powders

The morphology of surfactant-assisted mesoporous metal oxides was tuned to obtain high surface-area particles by utilizing the synthetic conditions for fabricating transparent thin films through an evaporation-induced self-assembly (EISA) process. For investigating their potential applications, especially for designing heterogeneous catalysts, mesoporous metal oxides should be obtained in powder forms; however, a serious limitation associated with their reproducibility persists. Herein, along with a rapid optimization approach, starting from determining and improving chemical composition for the fabrication of mesoporous metal oxide films, an advanced approach to obtain highly porous metal oxide powders is presented using a temperature-controlled spray-drying process with step-by-step but smooth optimization by combining several EISA processes, involving the utilization of a precursor solution optimized for a slow-drying process in the case of ceria (CeO2) using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO).

Aerosol-assisted synthesis of titania-based spherical and fibrous materials with a rational design of mesopores using PS-b-PEO

Surfactant-assisted synthesis is a promising technique for the tailor-made design of highly porous metal oxide based nanomaterials. There has been a demand for the comprehensive design of their morphology, porous structure and crystallinity to extend potential applications using metal oxide based materials such as titania (TiO₂). However, the porous structure is often deformed and/or destroyed during the process of crystallizing metal oxide frameworks. Herein, the aerosol-assisted synthesis of mesoporous TiO₂ powders was conducted in the presence of high-molecular-weight poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO), which improved the stability of the derivative mesoporous structure with an increase in the thickness of the TiO₂ frameworks. To propose a rational synthetic route for stable and porous metal oxides, the resultant mesoporous structure and the textural morphology of the mesoporous TiO₂ powders were surveyed using PS-b-PEO with different lengths of PS and PEO chains. By a judicious choice of the molecular structure of PS-b-PEO, the morphological design of the fully crystallized anatase phase of TiO₂ from spherical to fibrous ones was achieved with control over the mesopore diameter.

Accelerated crystallization of mesoporous Al2O3 powder recovered by spray-drying with a large amount of heated air

Crystallization into α-Al₂O₃ was accelerated with a large amount of heated air during spray-drying to recover mesoporous Al₂O₃ powders.