Preparation, Characterization and Catalytic Applications of $MoO_3$ Clusters Dispersed on $ZrO_2$

摘要

The synthesis, characterization and catalytic application of $MoO_3$(x mol%)-$ZrO_2$ catalyst with different composition is described. The $MoO_3$(x mol%)-$ZrO_2$ catalyst were prepared by pH controlled hydrolysis of the corresponding salt precursors. For the sake of comparison the catalysts were also prepared by conventional wet impregnation technique. The $MoO_3$(x mol%)-$ZrO_2$ catalyst were characterized by X-Ray diffraction, Scanning Electron Microscopy and Raman spectroscopy. XRD study indicate that the method of preparation plays an important role in controlling the phase transformation of the ZrO2. The tetragonal phase was found to be selectively stabilized in presence of MoO3 in case of the pH controlled precipitation method. The martensitic phase transformation of the monoclinic to tetragonal phase was accomplished at much lower temperature in presence of $MoO_3$ in $ZrO_2$ matrix. The particle size calculated using Scherrer’s equation was found to be in the range of 10-20 nm. Raman study conducted on the sample indicates the presence of various molecular species and clusters of $MoO_3$ on the surface of the $ZrO_2$. At least three type of molecular species such as MoO42-, Mo7O246- and Mo8O266- was observed on the surface of zirconia. The $MoO_3$(x mol%)-$ZrO_2$ materials were used as a efficient catalyst for the multicomponent condensation of aryl aldehydes, aryl ketones, acetic chloride and acetonitrile to yield the -acetamidoketones. The protocol developed in the study is advantageous in terms of recyclable catalyst, simple, high yielding, devoid of toxic chemicals and high purity of the products.udud