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Silica-Alumina-Supported Acidic Molybdenum Catalysts -TPR and XRD Characterization.-The role of the composition of various silica-alumina supports on the stability of Mo oxide catalysts and of solid state reaction products of Mo oxides and silica-alumina is investigated by XRD and TPR. The reducibility increases with increasing Mo loading regardless of the support composition. Low loading (≤ 4 wt.% MoO3) favors tetrahedral Mo species of low reducibility and high loading promotes octahedral, multilayered Mo species having high reducibility and a low-temp. TPR peak. Generally, the reduction of alumina-rich catalysts is much less than that of silica-rich ones. Crystalline phases of Mo are only formed on Mo-rich and silica-rich catalyst, e.g. orthorhombic MoO3 on 100% SiO2 and MoO3 and Al2 (MoO4)3 on Al2O3-containing silica. -(RAJAGOPAL, S.; MARINI, H. J.; MARZARI, J. A.; MIRANDA, R.; J. Catal. 147 (1994) 2, 417-428; Dep. Chem. Eng., Univ. Louisville, Louisville, KY 40292, USA; EN)