Performance of supported and unsupported Fe and Co catalysts for the direct synthesis of light alkenes from synthesis gas

Abstract A sustainable way to produce plastics made from biomass (biomass to gas) and electricity (power to gas) could be obtained by the direct synthesis of light alkenes. Samples (≤ 1 g) of the bulk catalysts Co/Fe, Fe/Na/S and the supported catalysts Fe/Mn | MgO and Co | SiO 2 are mentioned in the literature to allow the direct synthesis of light alkenes. These materials are studied in extended fixed beds with catalyst amounts between 35 and 70 g and classic syngas (H 2 and CO) in this work in order to prepare a potential scale-up of this technology. The influence of activation conditions (H 2 or CO as reduction agent; 350 or 420 °C at 1.5 bar) and synthesis temperature (230–500 °C) on catalyst activity and product selectivity are pointed out. Selectivities to ethene of up to 11% are found for Fe/Mn | MgO at T  ≈ 440 °C and for Fe/Na/S at T  ≈ 310 °C. The other materials did not produce significant amounts of ethene. CO 2 and CH 4 were the main products in any case, while C 2 H 6 was the main C 2 product. Applying CO as reduction agent was superior to activation with H 2 at low times on stream ( − 1 applied in this study, which facilitates the conversion of primary alkenes in secondary reactions. Recommendations on operational conditions of Fischer-Tropsch to olefins processes are specified.