Preparation of Fe/SAPO-34 catalyst and its performance in CO hydrogenation to light olefins

Abstract

Fischer-Tropsch synthesis is an important route to synthesize light olefins from syngas. However, precise control of the product selectivity and enhancing carbon utilization efficiency remains a challenge. Herein, a series of Fe/SAPO-34 catalysts with different Fe contents were prepared using negative pressure impregnation method, and their performance in CO hydrogenation reaction was evaluated. Combined N₂ adsorption/desorption, XRD, SEM, NH₃-TPD, and CO-TPD characterizations, the structure-performance relationship of the Fe/SAPO-34 catalysts was clarified. The results showed that with the increase of Fe loading, the strength and quantity of the acidity of the catalysts decreased sequentially, while the CO non-dissociation activation ability was weakened and the CO dissociation activation ability was enhanced, resulting in an increasing and decreasing trend in the selectivity of light olefins and oxygenates, respectively. Under a mild reaction conditions of t=200°C, p=2.0 MPa, GHSV=3300 h^–1, in the carbon products containing CO₂, the selectivity of light olefins and oxygenates over 5%Fe/SAPO-34 catalyst was 16.2% and 52.6%, respectively; while that over 25%Fe/SAPO-34 catalyst was 31.9% and 16.9%, respectively. A reasonable reaction mechanism was proposed based on the in situ IR characterization. This study provides a new way for the research and development of catalyst for light olefins synthesis with enhanced carbon utilization efficiency, showing promising application prospects.