A bifunctional Zn/ZrO2–SAPO-34 catalyst for the conversion of syngas to lower olefins induced by metal promoters

Abstract

Syngas (CO/H₂) was selected as a non-petroleum carbon source and transformed into lower olefins (C₂–C₄), aromatics (BTX), liquefied petroleum gas (LPG), and gasoline (C₅–C₁₁), respectively. The CO-precipitation method was used to synthesize different metal-doped Zn/ZrO₂-M (M = Ce, La, Mg, and Sr) catalysts. These catalysts were combined with SAPO-34 zeolite to investigate the catalytic performance in a high-pressure dual-bed fixed reactor. The catalysts were characterized by using XRD, N₂-adsorption, H₂-TPR, NH₃-TPD, CO₂-TPD, laser Raman, CO-TPD, XPS, and SEM techniques. Adding Ce promoter to the Zn–ZrO₂ catalyst improved the number of active sites, which were CO and H₂ adsorption sites, while weakening the interaction between Zn and ZrO₂. Due to its homogeneous element distribution, the Ce-doped Zn/ZrO₂ catalyst had superior catalytic performance. There was also a synergistic effect with Ce-doped Zn/ZrO₂ and SAPO-34 zeolite. Furthermore, the optimal Ce-doped Zn/ZrO₂–SAPO-34 bifunctional catalyst exhibited 20% CO conversion and 79% lower olefin selectivity while remaining stable for 100 h without activity loss. Because of its stable catalytic performance under industrially relevant conditions, the bifunctional catalyst is a promising candidate for industrial applications.