CRYSTALLIZATION OF MICROPOROUS ALUMINOPHOSPHATES AT HYDROTHERMAL AND ORGANOTHERMAL GONDITIONS

A. Norlund Christensen

Department of Inorganic Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark. anc@kemi.aau.dk

Keywords: Hydrothermal, organothermal, synthesis, microporous, aluminophosphates

Compounds with open framework structures as zeolites and microporous aluminophosphates are traditionally obtained in crystallization of amorphous gels in the temperature range 100-200^oC. The reaction media can be based on water or on organic solvents which then corresponds to hydrothermal or organothermal conditions, respectively. The amorphous aluminophosphate gels are made from aluminium isopropoxide, 85% phosphoric acid, an organic structure directing amine and the solvent water or ethylene glycol. The heat treatments are performed in pressure vessels with Teflon liners. The use of the mineralizer hydrofluoric acid can improve the size of the crystals obtained in the crystallization. The size of crystals obtained is realted to the nucleation rate and to the crystal growth rate in the reaction media, and these are a priori not the same at hydrothermal and organothermal conditions. In addition, the compositions of the crystalline microporous aluminophosphates are dependent upon the composition of the gels with respect to the molar ratios of the components and the structure directing template molecules present. X-Ray powder diffraction and single crystal diffraction analyses were used to identify the reaction products. A comparison will be made between results obtained at hydrothermal and organothermal crystallization conditions.