Controlled synthesis of cobalt nanocrystals on the carbon spheres for enhancing Fischer–Tropsch synthesis performance

Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine cobalt nano-particles was studied. Thermal decomposition synthesis method was applied to obtain cobalt catalysts with high dispersion and narrow particle size distribution. Furthermore the cobalt size can be controlled by the molar ratio of o-dichlorobenzene/benzylamine. Compared with supported cobalt catalysts prepared by incipient wetness impregnation method and ultrasonic impregnation method,the catalyst prepared by thermal decomposition method showed higher catalytic activity, higher long chain hydrocarbons selectivity and lower methane selectivity.

Design and construction of size-controlled CoO/CS catalysts for Fischer–Tropsch synthesis

The use of supported Co-based catalysts is widespread in various catalytic reactions due to their unique structures.The structural sensitivity of these catalysts is closely linked to their particle size and crystal form.Consequently,comprehending the structure–activity relationship requires the development of well-defined Co-based catalysts.Herein,we employed a colloidal wet chemical process and a heterogeneous nucleation method to prepare well-defined Co-based catalysts supported by inert carbon nanospheres.The nanospheres’surface possesses abundant functional groups that efficiently capture metal complexes and facilitate the nucleation and growth of CoO nanoparticles.By adjusting the Co source concentration,solvent molar ratio,and nucleation growth kinetics,we successfully prepared CoO/carbon sphere(CS)catalysts with different particle sizes and crystal forms.The influence of metallic face-centered cubic(fcc)-Co^(0) particle size in the range of 6.6–17.6 nm on the performance of Fischer–Tropsch synthesis(FTS)using well-defined CoO/CS catalysts has been investigated.The result demonstrated that the turnover frequency(TOF)remained constant for CoO/CS catalysts with metallic fcc-Co^(0) particle size larger than 7.7 nm.However,both the selectivity and the activity changed for CoO/CS catalysts with smaller particles(<7.7 nm).Significantly,when metallic fcc-Co^(0) particle size was reduced from 17.6 to 7.7 nm,the cobalt time yield increased to 6.7μmolCO·gCo^(-1)·s^(-1),indicating improved catalytic activity.At the same time,the CH_(4) selectivity decreased to 4.9%,suggesting a higher preference for hydrocarbon production.These findings demonstrate the importance of particle size in Co catalyzed Fischer–Tropsch synthesis.The use of well-defined CoO/CS catalysts offers valuable insights into the structure–activity relationship,leading to a better understanding of Co catalyzed Fischer–Tropsch synthesis.