Direct synthesis of lower eolefins from syngas via Fischer-Tropsch synthesis catalyzed by a dual-bed catalyst

Direct synthesis of lower olefins (C-2.4(-)) from syngas through Fischer-Tropsch synthesis (FTS) is a promising approach to satisfy increasing demand for such chemical feedstocks. However, control of selectivity remains a major challenge for the Fischer-Tropsch to olefins (FTO) process. Herein, we designed a dual-bed FTO catalyst FeZnNa/zeolites, which contained zeolites filled with a conventional FTS catalyst. We explored the catalytic performance of different zeolites in the dual-bed catalyst, namely HY, NaY, ZSM-5, SAPO-34, H beta, Li beta, Na beta, K beta, and Rb beta. The integration behavior and mass ratios of the two active components, and reaction parameters of the FTO process were also optimized. The highest selectivity of C-2.4(-) up to 50.5 %, and a high CO conversion of 92.9 %, were achieved for the FeZnNa/Na beta dual-bed catalyst. Importantly, the FeZnNa/Na beta catalyst had outstanding long-term stability with no obvious deactivation over 100 h of testing, making it a potential catalyst for industrial applications. The acidity and pore structure of the zeolite were found to be key factors for improving the yields of lower olefins from these dual-bed catalysts. The excellent catalytic performance of FeZnNa/Na beta is attributed to the suitable acidity and hierarchical pore structure of Na beta.