Sodium promoter on iron-based catalyst for direct catalytic synthesis of light alkenes from syngas

• Reduction commenced in syngas (H2/CO = 20) for 48 h.
• The appropriate content of sodium improved the selectivity of syngas to light olefins and avoided the decreasing of FTS activity.
• The maximum selectivity (22.4 mol.%) for C2=–C4= was observed with one of the Na-promoted catalysts in HTFT.

Direct catalytic conversion of syngas to light alkenes was carried out on sodium promoted FeMn catalysts by co-precipitation–calcination–impregnation method. N2-physisorption demonstrated that the addition of sodium decreased surface area. H2-TPR revealed that excessive sodium inhibited reduction of catalysts. XRD and MES results indicated that sodium made carburization easy. The results showed that the addition of Na/Fe in the range of 0.7–3.5 mol% could improve the light alkene selectivity in syngas conversion. A maximum in CO conversion and light olefin selectivity were noted upon increasing sodium content (2.8 mol% Na/Fe) and then declined.

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