Abstract: A series of Fe3O4 microspheres with controllable structures was prepared from ferric chloride by solvothermal reaction method with different preparation parameters (solvothermal reaction times, types of alcohols and carboxylate) and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and H2-TPR, separately to investigate the size of primary grains and secondary particles, their surface areas as well as reducibilities. The results indicate that by adjusting the preparation parameters, the size of primary grain can be controlled in the range of 5.6-25.1 nm, while the particle size of microspheres is in the range of 149-503 nm. With the decrease of grain size, the surface area of Fe3O4 microspheres increases and the reducibility is improved. It is found based on the test results of syngas to olefins that the decrease of the grain size increases the selectivity of lower olefins and decreases the CO2 selectivity. While the decrease of the microscopes particle sizes is favorable to improve CO conversion.

Key words: Fe3O4, microspheres, solvothermal reaction, lower olefins, syngas