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 and the characteristics of the framework structure of the molecular sieves were studied by means of IR and Raman spectroscopy. Decomposition of TEA and the formation of OH groups were investigated by DRIFT measurements carried out within the temperature range from 300 to 633 K. It has been found that TEA exists as triethylammonium ions in the as-synthesized samples, and its decomposition occurs via abstraction of ethylene and the stepwise formation of diethyl- and ethylammonium cations. The decomposition mode under a nitrogen atmosphere is different from that under air and requires another temperature. A thermal treatment of both molecular sieves at above 970 K results in a transformation of the structure. (C) 1997 Elsevier Science B.V.