Ionothermal Synthesis and Selective Oxidation Performance of a Crystalline Vanadium Phosphate Catalyst

Abstract

A new strategy for synthesizing vanadium phosphate with a lamellar and clubbed morphology was proposed, which involved a facile ionothermal process in a deep eutectic solvent. Firstly, NaVO3 and O–H3PO4 were heated in the eutectic mixture of urea and choline chloride to prepare a vanadium phosphate precursor. Then, the precursor was calcined in air at 733 K for 18 h to produce an active phase, which was used as a catalyst for the selective oxidation of cyclohexanol to cyclohexanone. It was found that the catalyst possessed a higher P/V atomic ratio than that of the counterpart prepared through the conventional hydrothermal synthesis method, which could prevent the over-oxidation of VIV to VV. Thus, the catalyst possessed a higher content of VIV and VIII oxidation states, which accordingly led to higher selectivity for cyclohexanone and a greater yield.