Dispersion and catalytic activity of MoO 3 on TiO 2 ‐SiO 2 binary oxide support

The authors present results of an investigation into the dispersion of MoO 3 on TiO 2 ‐SiO 2 composite and its reactivity in transesterification of dimethyl oxalate (DMO) with phenol to produce methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO). They examined the effects of support composition, MoO 3 content, and reaction time on activities of the transesterification. The results show that MoO 3 /TiO 2 ‐SiO 2 is more active and selective than MoO 3 /TiO 2 , MoO 3 /SiO 2 , and TiO 2 /SiO 2 catalysts in the transesterification reaction. The best catalytic performance is obtained over a 12%MoO 3 /8%TiO 2 ‐SiO 2 , providing a 71.8% DMO conversion and 59.0%, 40.1% selectivities for MPO and DPO, respectively. Through employing X‐ray diffraction and inductively coupled plasma‐optic emission spectrometry, they show evidence strongly suggesting that improvement of catalytic reactivity over the TiO 2 ‐modified SiO 2 support can be ascribed to the enhanced metal oxide support interactions and the increased dispersion capacity of MoO 3 phase. They also present evidence showing that incorporation of TiO 2 in SiO 2 can elevate the monolayer dispersion capacity of MoO 3 on SiO 2 . Thus, they conclude that increased DPO selectivity from MoO 3 /TiO 2 ‐SiO 2 catalysts can be primarily attributed to the improvement of MoO 3 dispersion and the synergistic effect between amorphous MoO 3 and amorphous TiO 2 . © 2008 American Institute of Chemical Engineers AIChE J, 2008