High temperature, high pressure ESR study of molybdenum-containing catalysts

Abstract

The reduction of molybdenum in molybdenum trioxide over various supports was studied using high-temperature, high-pressure ESR techniques. The support materials have a great influence on the reduction behaviour of the catalysts at high temperatures under a high pressure of hydrogen. The ease of reduction of molybdenum in the order MoO3/SnO2 > MoO3/ZrO2 > MoO3/TiO2 > MoO3/Al2O3 > MoO3/SiO2 > MoO3/MgO.To clarify the interaction between catalysts and reactants, the molybdenum-containing catalyst-9-methylanthracene system was monitored. An electron-transfer reaction from 9-methylanthracene to catalysts occurred and both organic radicals and Mo(V) species were observed at the same time. It was found that the behaviours of organic radicals and Mo(V) species depend on the support materials, i.e. the organic radical concentration increases with increasing Mo(V) concentration for the MoO3-Al2O3-9-methylanthracene system in the temperature range 381 – 558 K. On the other hand, the organic radical concentration is inversely proportional to Mo(V) concentration for the MoO3-ZrO2-9-methylanthracene system in the range 399 – 493 K.