Water-vapor-induced transformation of two-dimensional vanadyl hydrogen phosphate hemihydrate, VOHPO_4 centre dot 0.5H_2O, to one-dimensional tetrahydrate, VOHPO_4 centre dot 4H_2O

摘要

The catalytically important, two-dimensional vanadyl hydrogen phosphate hemihydrate, VOHPO_4 centre dot 0.5H_2O phase was transformed to the one-dimensional vanadyl hydrogen phosphate tetrahydrate, VOHPO_4 centre dot 0.5H_2O for the first time by mild treatment with water vapor. It was also observed that for three samples of VOHPO_4 centre dot 0.5H_2O prepared under different conditions, the rate of transformation to the tetrahydrate was markedly affected by morphology and crystallinity. The tetrahydrate phase could also be re-transformed to the hemihydrate by applying high vacuum or by heating at 120 deg C, but this was accompanied by significant loss in crystallinity.