THERMAL INVESTIGATIONS OF SOME ALPO AND MEAPO MATERIALS PREPARED IN THE PRESENCE OF HF

Hydrothermal synthesis of chabazite-like AlPO4 in a fluoride medium, u sing piperidine as the structure directing agent, is also successful i n the preparation of transition-metal-modified AlPO products. The tran sition metal (Co, Mn, and Ni) has no influence on the triclinic deform ation of the chabazite framework, formed by an interaction of fluoride ions with the AlPO framework. Upon calcination, successive destructio n of piperidine and fluoride bridges occurs. The calcined chabazite-li ke products exhibit a particular sensitivity for humidity resulting in a new triclinic deformation of the chabazite framework The deformatio n is completely reversible and can be removed by dehydration. The tran sition-metal incorporation exerts an influence on the dehydration proc ess. (C) 1997 Elsevier Science B.V.