Effects of metal-support interactions on the synthesis of methanol over palladium

Abstract

The synthesis of methanol and other products from CO and H 2 was studied over Pd catalysts prepared by adsorption of Pd(π-C 3H 3) 2 on MgO, ZnO, La 2O 3, γ-Al 2O 3, SiO 2, TiO 2, and ZrO 2 as well as over a SiO 2-supported Pd catalyst prepared from PdCl 2 and Pd black. Both the activity and selectivity of Pd were affected strongly by the nature of the support and the composition of the Pd precursor. The specific activity for methanol synthesis decreased in the order Pd La 2 O 3 ⪢ Pd SiO 2 [derived from PdCl 2] > Pd ZrO 2 > Pd ZnO ≈ Pd MgO > PdTiO 2 > Pd Al 2 O 3 ≈ Pd SiO 2 [derived from Pd(π-C 3H 5) 2] ⪢ Pd black, while the specific activity for hydrocarbon synthesis decreased in the order Pd TiO 2 ⪸ Pd ZrO 2 > Pd La 2 O 3 > Pd Al 2 O 3 ≈ Pd SiO 2 [derived from PdCl 2] ⪸ Pd SiO 2 [derived from Pd(π-C 33H 5) 2] ≈ Pd black ⪢ Pd MgO ⪸ Pd ZnO . Dimethyl ether production was observed over four of the catalysts and the activity for formation of this product decreased in the order Pd Al 2 O 3 ⪢ Pd TiO 2 ⪢ Pd MgO ≈ Pd ZrO 2 . The effects of support composition on the catalytic properties of Pd are discussed in the light of current ideas concerning metal-support interactions and the acid-base properties of the support.