Boosting the propylene selectivity over embryonic borosilicate zeolite catalyst for oxidative dehydrogenation of propane

Abstract

Boron-containing zeolites have been proven potential in catalyzing the oxidative dehydrogenation (ODH) process and the boron sites in open coordination are considered as the active center. By considering the diversity and adjustability in the crystal structure of zeolite, there is a great opportunity to further tune the activity and selectivity. Herein, the embryonic borosilicate zeolite with abundant defective sites and developed large porosity is prepared for catalyzing ODH of propane reaction. An ∼ 20 % improvement in propylene selectivity is achieved at propane conversion of 21.5 % at 540 °C, with propylene productivity nearly an order of magnitude higher compared with crystalline MFI-type borosilicate zeolite. Solid-state NMR reveals the formation of boron sites in open coordination derived from the defect-rich structure of embryonic borosilicate zeolite, guaranteeing ample exposure of the active center. Combined with kinetic measurements, the reaction in the gas phase initiated by the active boron sites is mainly responsible for the high catalytic performance in ODH of propane reaction. The designed experiment indicates the strengthened gas-phase reaction facilitates the activation of propane, consequently resulting in the increase of reaction order of propane from 1.06 to 2.30. This work reveals the significant role of gas-phase reactions during the ODH of propane reaction and provides a new insight for boosting the propylene selectivity of zeolite-based catalysts.