CATALYTIC ACTIVITY AND SI, AL, P ORDERING IN MICROPOROUS SILICOALUMINOPHOSPHATES OF THE SAPO-5, SAPO-11, AND SAPO-37 TYPE

The catalytic activity in the conversion of decane on SAPO-5, SAPO-11, and SAPO-37 samples with Si T-atom fractions ranging from 1 to 42% were determined. The relationship of catalytic activity with compositional parameters is discussed. Due to the nonuniform distribution of silicon, aluminium, and phosphorus over individual crystals, the overall chemical composition of a SAPO-n sample is unable to rationalize its catalytic activity. In order to explain the catalytic activity of SAPO-5, SAPO-1 l, or SAPO-37 materials, the contributions of aluminosilicate (SA) and silicoaluminophosphate (SAPO) crystal domains have been determined using 29Si MAS NMR. Acid sites located in the SA and SAPO domains and at their interphases contribute to the catalytic activity. The contribution of the different types of acid sites to the catalytic activity is strongly dependent on the SAPO-n structure type. © 1990.