LaCO3OH Nanoprisms: Photoluminescence and toxic NOx reduction properties

Nitrogen oxides (NOx = NO + NO2) emitted from both mobile and stationary combustion devices have been increasing and causing serious environmental problems, such as global warming, acid rain and photochemical smog, and air pollution. Indeed, prolonged exposure to NOx can cause violent coughing, difficulty in breathing, and cyanosis; it could be fatal. Currently, NOx reduction by ethylene, propane, propylene, and n-octane hydrocarbons have been investigated in presence of O2. In this regard, methane (CH4) is a good candidate; however, it is hard to activate CH4 due to the very strong C-H bond, which requires high reaction temperatures. It is highly desirable to use CH4 as a reducing agent because of its low cost and easy obtainability. Thus, NOx reduction with CH4 at relatively high temperatures have high demand in the field of de-NOx (decomposition-NOx) catalysts. The selective catalytic reduction (SCR) of NOx with CH4 have been tested and it was claimed that an increase in methyl radical concentration might enhance the reaction activities. It was assumed that the methane oxidative coupling is responsible for this kind of catalytic systems. Actually, the real reaction mechanism of NOx reduction with CH4 in the presence of oxygen over metal oxide remain unclear. In this project, we will use metal oxide based catalysts for NOx reduction, which is found promising due to their high hydrothermal stability. Metal oxides are inexpensive in comparison with noble metal (Pt, Pd and Ru)-based catalysts. In this work, single-crystalline large-scale LaCO3OH nanoprism morphologies will be synthesized by controlling La and Ca molar ratio. Our recent on-going research results revealed that a large-scale production of phase-pure hexagonal LaCO3OH nanoprisium can be prepared using a simple and environmental friendly hydrothermal method. This new synthesis route provides a novel and general approach to the synthesis of rare-earth compounds with a variety of morphologies and properties that does not require the assistance of templates or catalysts. The photoluminescence (PL) properties of the as-synthesized powders will be examine because the nanoprisms has smooth surface morphology, well-defined sizes and shapes. In addition, NOx reduction activity will be examine over highly dispersed CaO containing La2O3 , which will be obtain after calcination the LaCO3OH at 800 C for 2h. The CaO containing La2O3 catalysts with different composition of La:Ca have potential to show high performance for NOx reduction with CH4 in presence of O2 and H2O vapor. Because La2O3 alone and/or CaO alone showed high NOx reduction activities with CH4. Finally, the CaO containing La2O3 catalysts will be coated over honeycombs and examined the NOx reduction activity in presence of 10% H2O vapour and SO2 at high space velocity for real application.