Support effect in hydrogenation of methyl benzoate over supported manganese oxide catalysts

Manganese oxide supported on MgO, gamma-Al(2)O(3), SiO(2), ZrO(2), TiO(2) and SiO(2)-Al(2)O(3) catalysts were prepared. The effect of support on their catalytic behavior for hydrogenation of methyl benzoate tobenzaldehyde was studied. The formation of toluene is suppressed on the supported catalysts due to the dilution of oxygen vacancies on the catalyst surface. The benzaldehyde yield of the supported catalysts follows the trend Mn/gamma-Al(2)O(3) > Mn/TiO(2) > Mn/ZrO(2) > Mn/SiO(2)-Al(2)O(3) > Mn/SiO(2) > Mn/MgO. XRD measurements show that the Mn nitrate precursor is essentially transformed to highly dispersed MnO(2) on the supports at calcination and subsequently to MnO under reaction conditions with an exception of Mn/MgO. TPR and XPS analyses suggest that a strong interaction between manganese oxide and the gamma-Al(2)O(3) support plays a positive role in the hydrogenation reaction. (C) 2003 Elsevier Science B.V. All rights reserved.