Vapor-phase Beckmann rearrangement of cyclohexanone oxime over H 3PO 4/ZrO 2–TiO 2

Abstract

ZrO 2–TiO 2 mixed oxides with a Ti and Zr molar ratio of 1/1 were prepared under various conditions by the sol–gel method. Catalysts containing 5–35% H 3PO 4 were prepared using these oxides and the catalytic performance of each material for vapor-phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam was determined. As the H 3PO 4 content in the mixed oxide increased, the specific surface area decreased; XRD results indicated that ZrO 2–TiO 2 became amorphous after calcinations at 700 °C. The yield of lactam increased with increasing the H 3PO 4 content in the mixed oxide and reached a maximum value for the 15 wt.% H 3PO 4 on the ZrO 2–TiO 2 (1/1) support. With further increase in H 3PO 4 content, the lactam yield decreased; the lowest value was observed for the 35 wt.% H 3PO 4 on the ZrO 2–TiO 2 (1/1) support. The acidic properties and the pore characteristics of the catalysts were key factors that affected its performance. The influences of the operating parameters on the performance of H 3PO 4/ZrO 2–TiO 2 (1/1) catalyst were also investigated. The interaction of H 3PO 4 with ZrO 2–TiO 2 (1/1) support has been investigated by FT-IR, for characterization of the interaction of H 3PO 4 with the support.