Exfoliated VOPO 4·2H 2O dispersed on alumina as a novel catalyst for the selective oxidation of cyclohexane

Abstract

The VOPO 4·2H 2O phase has been exfoliated in 2-propanol and the exfoliated solution dispersed on alumina in the ratio 1:1 (VPO-ED). A sample of exfoliated VOPO 4·2H 2O was also obtained by recovering the solid from the exfoliated solution of VOPO 4·2H 2O (VPO-E). Both these samples were characterized by XRD, FTIR, TGA/DTA, and SEM studies and it was shown that VPO-ED and VPO-E have the original VOPO 4·2H 2O structure although the morphology, crystallinity and crystal size and surface areas of the samples are affected both on exfoliation and subsequent dispersion on alumina. These phases have been shown to be active catalysts for the oxidation of cyclohexane preferentially to cyclohexanol. The conversion of cyclohexane increased markedly in the case of the sample dispersed on alumina. Thus, using VPO-ED as the catalyst, a cyclohexanol/cyclohexanone ratio of 71 can be obtained even at a high cyclohexane conversion of 83.3%. The present work therefore not only represents a novel approach for preparing dispersed VPO phases but also demonstrates the efficiency of the VOPO 4·2H 2O phase in catalyzing the oxidation of cyclohexane selectively to cyclohexanol.