PREPARATION OF LAYERED ALPHA-ZIRCONIUM PHOSPHATE WITH A CONTROLLED DEGREE OF HYDROLYSIS VIA DELAMINATION PROCEDURE

The hydrolysis of α-Zr(HPO4)2 · H2O has an appreciable influence on its ion exchange, intercalation, proton conductivity, and catalytic properties; it is furthermore of importance for the preparation of pillared porous materials. Direct hydrolytic attack in alkaline media can be carried out only for the surface phosphate groups of the layered crystals. To overcome this difficulty the crystals were first delaminated by an intercalation of methylamine; the colloidal dispersion was left 24 h to hydrolyze at fixed pH value (in the range 9-12) and finally, after regeneration in H form by acidification, the hydrolyzed Zr(HPO4)2-x-(OH)2x · n H2O materials were separated from the solution. The hydrolytic cycle can be repeated several times if high degrees of hydrolysis are desired; however, the stability of the α layer was found to be seriously compromised for high degrees of hydrolysis, and amorphous products were generally obtained for x values higher than 0.8-0.9. © 1993 Academic Press. All rights reserved.