TRANSFORMATION OF ISOPROPANOL OVER PT/HXVMOO5.5 HYDROGEN BRONZE

The transformation of isopropanol was studied at 423 K over a mixed molybdenum-vanadium oxide, with and without platinum as well as over the corresponding hydrogen bronze prepared via hydrogen spillover. In the absence of platinum, dehydration is the main reaction. However, propane and acetone are produced in small amounts, which points to the acid-base character of the oxide and to the existence of distinct hydrogenation sites. For the Pt/oxide system, higher conversions and acetone selectivities over 90% are obtained. A marked deactivation with time is noted, which is probably due to the continuous modification of the oxide surface and of the metal oxide contact. The hydrogen bronze of the mixed oxide exhibits a much improved activity and stability. Without platinum, switching from helium to hydrogen as carrier gas has a slight influence on the selectivity whereas for Pt/oxide, both activity and acetone selectivity are affected. The influence of temperature on the reaction was studied over the hydrogen bronze. The effect is different below and above 373 K and is related to the hydrogen stoichiometry of the bronze, the bronze with the lower stoichiometry (lacunar bronze) being the most active catalyst.