2. EXPERIMENTAL
2.1 Catalyst preparation
The meso-macroporous SiO2 monoliths were prepared by a sol-gel method similar with our previous studies31,32. By controlling the rates of phase separation and sol-gel process, the interconnected macropores with various diameter were obtained, while the mesopores were from ammonia etching. The prepared meso-macroporous monoliths were ground into 10-20 mesh as supports and labeled as S0, S50, S150, S280, S440, S1100, S2100 and S6000 respectively according to the diameter of the macropores. A series of cobalt catalysts with the same nominal cobalt loading (15 wt %) were prepared by incipient impregnation method. The obtained supports were impregnated with cobalt nitrate and calcined at 400°C for 6 h after drying at 60°C for 2 h and at 120°C for 4 h successively. The obtained catalysts were labeled as Co/S0, Co/S50, Co/S150, Co/S280, Co/S440, Co/S1100, Co/S2100 and Co/S6000 respectively.
2.2 Catalyst characterization
The textural properties of the samples were obtained combining the N2 adsorption-desorption isotherms measured by an ASAP-2000 Micromeritics instrument and mercury intrusion isotherms measured using a MicroActive AutoPore Iv 9510 analyzer.
The morphological analysis of the obtained silica monoliths and the prepared catalysts were performed using a JSM-7001F scanning electron microscope (SEM) operated at 5.0-15.0 kV and using a JEM-2010F microscope operated at 200 kV respectively.
X-ray diffraction (XRD) characterization was carried out on a PANalytical Empyrean X’pert powder diffractometer operated at 50 kV and 50 mA with Cu Kα radiation.
H2 temperature-programmed reduction (H2-TPR) was performed to obtain reduction profiles of the prepared catalysts using a Zeton Altamira AMI-200 unit. The detailed sample pretreatment, data processing and operation method are the same with our previous report 32.
2.3 Catalyst testing
0.5g of the prepared catalyst (10-20 mesh) diluted with an equal volume of quartz sand, was evaluated in a lab-scale fixed-bed stainless steel reactor (Φ10×500 mm). The other detailed setup used for FTS experiments, including methods and tools, was described in our previous literature32.