SYNTHESIS AND CATALYTIC PROPERTIES OF SUBSTITUTED ALPO4-31 MOLECULAR-SIEVES

Molecular sieve AlPO4-31 and substituted analogues (MnAPO-31, SAPO-31, MnAPSO-31) have been tested for their catalytic properties in the iso merization of 1-butene over 6 h time on stream at 743 K. The conversio n of 1-butene proceeds selectively by either double bond or skeletal i somerization. MnAPSO-31 with a molar MnO/P2O5 ratio adjusted to 0.01 y ields the highest percentage of isobutene whereas the parent AlPO4-31 leads almost completely to a double bond shift with only minor skeleta l isomerization. The results are related to the acidity characteristic s that were determined by ammonia thermodesorption. Deactivation is ac companied by a loss of selectivity for the skeletal isomerization.