Studies of high surface area PtMoO3 and PtWO3 catalysts for selective hydrogenation reactions I. Preparation and characterization of catalysts by X-ray diffraction, transmission electron microscopy, hydrogen consumption and carbon monoxide chemisorption O

Ultrafine MoO3 and WO3 particles have been prepared in a flame reactor. Optimizations of reactor parameters allowed one to obtain high surface area (≥40 m2 g−1) orthorhombic MoO3 and monoclinic pseudo-orthorhombic WO3, after a calcination in air at 673 K to eliminate residual chlorine. Platinum loaded (0.1–0.2 wt.−%) catalysts supported on these oxides were characterized by volumetric measurements of H2 consumption, CO chemisorption, transmission electron microscopy and X-ray diffraction (XRD). In the presence of H2, hydrogen bronzes of MoO3 and MO3 were formed by the so-called hydrogen spillover process. In the range 298–673 K, the value of x in HxMoO3 bronzes lay between 1.44 and 2.10 whereas that of y in HyWO3 ranged from 0.44 to 0.58. Platinum was well dispersed on MoO3 or WO3 and a partial reduction of the supports as a result of H2 treatments at 673–773 K was shown by XRD.