DECOMPOSITION OF TEMPLATE IN SAPO-5 AND ALPO4-5 MOLECULAR-SIEVES STUDIED BY IR AND RAMAN-SPECTROSCOPY

The state of the triethylamine (TEA) template in AlPO4-5 and SAPO-5 an d the characteristics of the framework structure of the molecular siev es were studied by means of IR and Raman spectroscopy. Decomposition o f TEA and the formation of OH groups were investigated by DRIFT measur ements carried out within the temperature range from 300 to 633 K. It has been found that TEA exists as triethylammonium ions in the as-synt hesized samples, and its decomposition occurs via abstraction of ethyl ene and the stepwise formation of diethyl- and ethylammonium cations. The decomposition mode under a nitrogen atmosphere is different from t hat under air and requires another temperature. A thermal treatment of both molecular sieves at above 970 K results in a transformation of t he structure. (C) 1997 Elsevier Science B.V.