Partially reduced molybdenum trioxide deposited on titania under hydrogen at 673 K for 12 h ena- bled to convert several surface atomic layers to the catalytically active bifunctional (metal-acid) MoO2-x(OH)y/TiO2 (Mo...Partially reduced molybdenum trioxide deposited on titania under hydrogen at 673 K for 12 h ena- bled to convert several surface atomic layers to the catalytically active bifunctional (metal-acid) MoO2-x(OH)y/TiO2 (MoTi) structure. The formed metallic function is the result of π bonding between adjacent Mo-Mo atoms placed along the C-axis of the rutile structure of MoO2. Delocalization of these π electrons produces a wire like atomic metal. This resembles in a way, the small Pt particles deposited on a support. Moreover, dissociated hydrogen atoms are bonded to sample surface oxygen to produce Brønsted acid Mo-OH function(s). These metal-acidic properties have been tested for several catalytic reactions requiring one or bothcatalytic functions. In this order, 2-propanol species could be considered as a model test of the acidic function via dehydration of the molecule to propene, while hydrogenation of the produced propene to propane is performed by the metallic function. Moreover, hydrogenation of 2-propanol to acetone, requires relatively strong metallic function. In this order, addition of small amount of alkali metal like rubidium will suppress the acidic function in MoO2-x(OH)y/TiO2 and enhance the metallic function strength. The performance of the metallic function alone in this case will be evaluated. Titanium dioxide is employed in this catalytic system as a support. It does not have any catalytic effect. Association of XPS-UPS, ISS sur-face techniques with catalytic performances of this catalytic MoTi system will be presented.展开更多
文摘Partially reduced molybdenum trioxide deposited on titania under hydrogen at 673 K for 12 h ena- bled to convert several surface atomic layers to the catalytically active bifunctional (metal-acid) MoO2-x(OH)y/TiO2 (MoTi) structure. The formed metallic function is the result of π bonding between adjacent Mo-Mo atoms placed along the C-axis of the rutile structure of MoO2. Delocalization of these π electrons produces a wire like atomic metal. This resembles in a way, the small Pt particles deposited on a support. Moreover, dissociated hydrogen atoms are bonded to sample surface oxygen to produce Brønsted acid Mo-OH function(s). These metal-acidic properties have been tested for several catalytic reactions requiring one or bothcatalytic functions. In this order, 2-propanol species could be considered as a model test of the acidic function via dehydration of the molecule to propene, while hydrogenation of the produced propene to propane is performed by the metallic function. Moreover, hydrogenation of 2-propanol to acetone, requires relatively strong metallic function. In this order, addition of small amount of alkali metal like rubidium will suppress the acidic function in MoO2-x(OH)y/TiO2 and enhance the metallic function strength. The performance of the metallic function alone in this case will be evaluated. Titanium dioxide is employed in this catalytic system as a support. It does not have any catalytic effect. Association of XPS-UPS, ISS sur-face techniques with catalytic performances of this catalytic MoTi system will be presented.
