Structure and Reactivity of Molybdenum Oxide Catalysts Supported on La₂O₃-Stabilized Tetragonal ZrO₂

Abstract

A series of molybdenum oxide catalysts with Mo loadings in the range 2.5−12.5 wt % Mo supported on La2O3-stabilized ZrO2 was prepared by impregnation. X-ray diffraction results of the catalysts showed the diffraction patterns of crystalline MoO3 from 10 wt % Mo. Dispersion of molybdena was determined by the oxygen chemisorption method, and it was found to decrease with an increase in Mo loading due to formation of MoO3 crystallites at higher Mo loadings. Temperature-programmed reduction results suggest that the reducibility is found to decrease with Mo loading as a result of the decrease in dispersion. The acidity of the catalysts was found to increase with Mo loading, and the activity of the catalysts also found to increase with the increase in Mo loading up to 7.5 wt % Mo loading. Laser Raman spectra of the catalysts show the Raman bands due to MoO3 from 7.5 wt % Mo at 819 and 997 cm-1. At lower Mo loadings, highly dispersed species were observed. The catalytic properties were evaluated during the ammoxidation of toluene to benzonitrile and were related to the oxygen chemisorption sites on the support surface.

Ni nanoparticles highly dispersed on ZrO2 and modified with La2O3 for CO methanation

“…It was reported that La 2 O 3 can stabilize zirconia and can improve the antisintering ability of zirconia effectively. 33,34 No obvious change can be seen for 20LN-Z aer reduction and aer stability test, suggesting that Ni nanoparticles were still highly dispersed on the ZrO 2 aer long time test at high temperature. However, for the used 20L-N-Z-imp, the intensity of Ni diffraction peak increases (the inset in Fig.…”

High Thermal Stability of La2O3- and CeO2-Stabilized Tetragonal ZrO2

“…Solid solution formation, generally achieved by introducing larger isovalent cations (e.g., Ce 4+ ) or by doping aliovalent cations (e.g., La 3+ , Y 3+ , Sc 3+ , Pr 3+ , Mg 2+ , and Ca 2+ ) ,− into the ZrO 2 lattice, has been established as an effective way to enhance the thermal and kinetic stability of ZrO 2 into tetragonal phases at room temperature. These cations are believed to substitute for Zr 4+ in the cation framework, thus creating oxygen vacancies for charge compensation …”

Nanostructured Molybdenum Oxides from Aluminium-Based Intermetallic Compound: Synthesis and Application in Hydrogen Evolution Reaction

“…Due to the variable oxidation states of molybdenum, tuning of the crystal structure, morphology and oxygen vacancy is facilitated, which makes its oxide compounds suitable for electrochemical activities. Synthesis and analytical detection of numerous vital molecules has been successfully achieved using molybdenum oxide-based heterogeneous catalysis [ 7 , 17 ]. As gas sensors, molybdenum oxides have been well applied to NO, NO 2 , CO, H 2 , NH 3 , and other gases [ 1 , 5 ].…”