Two step synthesis and characterization of thermally stable hexagonal zirconium phosphate

摘要

Thermally stable hexagonal zirconium phosphate has been synthesized by a two-step method in which hexagonal zirconium sulfate surfactant composite is first produced by surfactant-assisted method and then subsequently treated in H_3PO_4 for long term. The 31P MAS NMR spectra show that the connectivity of phosphorus atoms increases from one ((Zr-O)PO_3) or two ((Zr-O)_2PO_2) to three ((Zr-O)_3PO) or four (P-O-P) upon calcination. There exists a significant number of surface Bronsted acid sites (Zr-O)_3POH on calcined sample. The high thermal stability of hexagonal zirconium phosphate is due to (Zr-O)_3PO and P-O-P connections, which build a network of zirconium phosphate.