Preparation of catalyst precursors for selective oxidation of n-butane by exfoliation–reduction of VOPO 4·2H 2O in primary alcohol

Abstract

A new method through intercalation and exfoliation of VOPO 4·2H 2O crystallites in primary alcohol (1-propanol or 1-butanol), followed by reduction with the alcohol, have been investigated for the preparation of catalyst precursor. Lamellar compounds, consisting of V 4+, P 5+ and alkyl group with thin film-like morphology, were formed and was characterized by means of XRD, IR, TG/DTA, and elemental analysis. The chemical formula of the precursor obtained by exfoliation–reduction in 1-butanol was shown to be VO{( n-C 4H 9) 0.16H 0.84}PO 4·0.8H 2O. On the other hand, a direct reduction of VOPO 4·2H 2O in the alcohol gave a mixed phase shown by (VOHPO 4·0.5H 2O) 0.3(VO{( n-C 4H 9) 0.3H 0.7}PO 4·3H 2O) 0.7 comprising plate-like microcrystallites. These precursors transformed to (VO) 2P 2O 7 phase during an activation process at 703 K in the presence of a mixture of n-butane 1.5% and O 2 17% in He balance. The obtained (VO) 2P 2O 7 through the exfoliation–reduction was well crystallized and consisted of thin flaky crystallites. It was found that (VO) 2P 2O 7 thus prepared through the exfoliation–reduction was highly active and selective for oxidation of n-butane.