The gas-phase synthesis of anisole from methanol and phenol is currently recognized as the process with the most theoretical research value and industrial application prospect. LaPO4has attracted widespread attention due to its excellent catalytic activity, robust water resistance, and high-temperature performance. In this work, rod-like monoclinic, mixed phase, and hexagonal LaPO4were synthesized using the hydrothermal method, and their catalytic activity was evaluated. The results showed that the catalytic activity of the hexagonal phase is higher than that of the monoclinic phase. By combining relevant characterization methods and DFT theoretical calculations, it is clarified that the higher acidity and stronger alkalinity of the exposed surface of hexagonal LaPO4are the main reasons for its higher activity. Further research has revealed that the main cause of LaPO4deactivation is carbon deposition on the catalyst surface.
The behavior of nanoparticles in media of different refractive index has received considerable theoretical and experimental investigation. However, the behavior of larger particles, of micron size, has not been established. We have chosen Eu 3+ as a marker of environmental changes. Dilution of this ion into LaPO 4 gives a simple, fingerprint emission spectrum which has been studied via its luminescent lifetime, the R 2 (( 5 D 0 → 7 F 2 )/( 5 D 0 → 7 F 1 ) intensity ratio) and the electric dipole:magnetic dipole intensity ratio, (ED:MD), of spectral features. Measurements of micron-sized particles of LaPO 4 :Eu 3+ synthesized by several methods have been made for dispersions in alcohols, in compressed glass discs, in melted glass discs, in phosphor in glass (PiG) and in melted PiG. The experimental results are discussed and rationalized. The Eu 3+ 5 D 0 emission lifetime is reasonably constant in the bulk powders, powders dispersed in alcohols or compressed discs but is smaller in PiGs and melted glass discs. In the PiGs the structural integrity of LaPO 4 :Eu 3+ is maintained until they are melted at higher temperature. The change in lifetime, when varying the composition of the PiG, follows the Virtual Cavity Model. For dispersal of the particles in solvents there is a cut-off particle size below 1 μm where the electronic spectra of the moiety become insensitive to the environment and the properties are determined by refractive index. The remarkable change in R 2 ratio in the different systems considered – by a factor of nearly 600 % - and the corresponding decrease in 5 D 0 lifetime – by a factor of nearly 60 % - illustrates the versatility of the lanthanide ion.
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