Synthesis and catalytic properties of substituted AlPO4-31 molecular sieves

Abstract

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