The effect of magnesium embedded into NiAPO-11 zeolite on enhancing its catalytic performance of 2-butene skeletal isomerization

Abstract

The distribution of acidic sites in molecular sieves has a decisive impact on catalytic skeletal isomerization of 2-butene. Accurately adjusting the acidic site to meet high selectivity and stability of the catalyst is crucial. Herein, magnesium embedding into NiAPO-11 zeolite was prepared by static hydrothermal method. The introduction of magnesium increased the proportion of weak Brønsted acid, resulting in a significant enhancement of catalytic activity. When the molar ratio of magnesium to aluminum oxide was 0.2:1, Mg-NiAPO-11 exhibited the best catalytic performance with the conversion of 2-butene being 65.06 % and the selectivity of isobutene being 71.02 %, which was comparable or even better than those reported previously. Furthermore, Mg-NiAPO-11 had good stability. The conversion of 2-butene only decreased by 3 %, while the selectivity of isobutene increased by 8 % during the 72-h reaction. Obviously, it was found that a small amount of carbon deposition led to an increase in the relative amounts of weak Brønsted acid, which resulting in an increase in the selectivity of isobutene. Our work put forward an effective strategy for accurately tuning the acidic sites of molecular sieves to effectively catalyze 2-butene to isobutene.