Highly dispersed and stable NiSn subnanoclusters encapsulated within Silicalite-1 zeolite for efficient propane dehydrogenation

Abstract

Propane dehydrogenation (PDH) is one of the most effective methods for intentional (“on-purpose”) propylene production. Isolated Sn sites on open supports exhibit considerable PDH performance comparable to that of industrial Pt- and Cr-based catalysts, but the loss of Sn is inevitable. Herein, highly dispersed and stable NiSn subnanoclusters encapsulated within the channels of silicalite-1 zeolite are fabricated through a one-step hydrothermal synthesis in this work. The as-prepared Ni1Sn1@S-1 zeolite catalyst exhibits outstanding PDH performance with considerable propylene formation rate (ca. 12.3 mmol∙gcat-1∙h−1) and high propylene selectivity (>88 %). Most significantly, no Sn loss is detected after three regeneration cycles. Structural elucidation of NiSn sites on catalysts, by HRTEM, H2-TPR, FTIR and XPS characterizations confirms that the Ni sites embedded in the geminal silanols of zeolitic framework play a vital role in anchoring Sn species and preventing the active sites from losing and sintering. The cooperative action of robust NiSn subnanoclusters is conducive to the selective C–H activation and the propylene desorption. A plausible dehydrogenation mechanism is revealed by in situ infrared spectroscopy. This study on siliceous zeolite confined NiSn catalysts delivers an insight into the nature of selective and stable NiSn sites involved in the PDH reaction.