Abstract
The authors present results of an investigation into the dispersion of MoO~3~ on TiO~2~βSiO~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~βSiO~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~βSiO~2~, providing a 71.8% DMO conversion and 59.0%, 40.1% selectivities for MPO and DPO, respectively. Through employing Xβray diffraction and inductively coupled plasmaβoptic emission spectrometry, they show evidence strongly suggesting that improvement of catalytic reactivity over the TiO~2~βmodified 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~βSiO~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~. Β© 2008 American Institute of Chemical Engineers AIChE J, 2008