Direct conversion of syngas to aromatics is of great significance to alleviate the shortage of petroleum resources. Herein, a Na modified Fe based catalyst was prepared, which could promote the synthesis of light olefins as intermediates for subsequent aromatization, achieved considerable high CO conversion and value-added aromatics selectivity after integrating it with HZSM-5 zeolite. Nevertheless, the deactivation of Fe based composite catalyst remains to be a challenge, especially for the catalysts in close proximity, which could deactivate in short period due to the lower aromatization ability of zeolite. Through various characterizations including XPS, XRF, TEM-EDS, NH3-TPD and Py-IR, the migration of alkali metal elements from the surface of Fe based catalyst to zeolite was discovered, and it was determined as one of the main reason for the deactivation of composite catalyst. During reaction process, the macro structure of Fe based catalyst could partly pulverize under the effect of phase variation and adsorbed on zeolite surface. The alkali metal in Fe based catalyst is prone to ionize and release electron, which could interact with Lewis acid sites on zeolite surface, lowering down the zeolite activity. This process could be inhibited by controlling the catalyst particle size, adjusting the alkali metal content in iron-based catalyst and enhancing the surface acidity of the zeolite, thereby prolong the catalyst stability over 120 h, providing a unique view for the design of composite catalyst in aromatic synthesis reaction.

The Promotion and migration of alkali metal on a well-designed Fe based composite catalyst for aromatic one-step synthesis reaction

ACS Spring Meeting 2021

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