Effect of Mn and reduced graphene oxide for the Fischer–Tropsch reaction: an efficient catalyst for the production of light olefins from syngas

Abstract

In this work, we demonstrate an efficient and high-performance catalyst for the production of light olefins from synthesis gas employing manganese (Mn)-mediated graphene oxide. First the CO hydrogenation reaction was catalyzed using bimetallic alumina supported-cobalt-manganese catalysts with various ratio of cobalt to Mn (1:1, 1:2, 1:3, 2:1 and 3:1). After the determination of the effect of different ratios on C2–C4 light olefin production, the efficiency of nanoporous graphene and reduced graphene oxide as support at an optimum ratio of bimetallic Co–Mn/Al2O3 catalyst were evaluated. The catalysts were characterized by BET, TPR, FTIR, RAMAN, TGA, XRD, FESEM, ICP, and XPS measurements. The reactions carried out in a fixed bed reactor under the constant condition (320 °C, atmospheric pressure, H2/CO = 1). It was identified that light olefin selectivity of the catalysts varies with different ratios. By increasing of the amount of Mn up to 1, methane formation decreased and light olefin selectivity increased. Conversely, with the further increase of the amount of Mn, light olefin selectivity decreases. This phenomenon is attributed to varying the degrees of Mn incorporation in the Co3O4 particles, which causes different degrees of reduction limiting the available metallic Co surface area. Also, the advantages of reduced graphene oxide supported nanoparticles (NPs) included higher conversion and C2–C4 light olefin selectivity in comparison with the graphene supported catalyst. The obtained results from the TPR revealed that the NPs reducibility was higher for the RGO supported catalyst. An increase of selectivity and conversion of Co–Mn/RGO catalyst is likely due to altering the surface interactions of NPs with the functional groups on reduced graphene oxide which was confirmed with XPS, FTIR and Raman analyses.