Soft chemical transformation of α-MoO3 to β-MoO3 as a catalyst for vapor-phase oxidation of methanol

Abstract

Abstract Monoclinic molybdenum trioxide, β-MoO 3 , was synthesized as an active catalyst for vapor-phase oxidation of methanol by a soft chemical transformation of α-MoO 3 . The addition of HNO 3 to an aqueous solution of α-MoO 3 , followed by drying and calcination, resulted in the formation of yellow powders consisting of β-MoO 3 . The β-MoO 3 content increased with the amount of HNO 3 , but the addition of excess HNO 3 inhibited β-MoO 3 formation. The maximum yield was obtained at a HNO 3 /Mo molar ratio of 0.37. Thermal analyses indicated that HNO 3 controlled dehydration of the dried precursor to induce β-phase formation. The resulting β-MoO 3 had a higher activity than α-MoO 3 in the partial oxidation of methanol to formaldehyde at temperatures below 600 K.