Fischer-Tropsch synthesis over cobalt supported on silica hollow sphere catalyst

Abstract

A propose of this work studied the silica hollow sphere (SHS) for a proper characteristic of support in the Fischer-Tropsch synthesis (FTS) because the normally main problem of FTS reaction was being produced the broader hydrocarbon products on a commercial catalyst. Nevertheless, the hollow sphere shape of SHS catalyst had a wall of the core catalyst for steric restriction of hydrocarbon propagation. The cobalt metals were loaded on the SHS by wetness impregnation method and used in the FTS. The SHS was synthesized through emulsion process with water/oil/water (W/O/W) that used the sodium silicate for silica source and NH4HCO3 for the mesopore generating in the SHS support. The proper SHS catalyst in FTS showed higher specific surface area more than 500 m2/g and less micropore, causing diffusion elimination and mass transfer inside the pore, which resulted in the enhanced CO conversion more than 90 percent, lower C12+, and the narrower hydrocarbon selectivity. Moreover, the study of the coated zeolite that was ZSM-5 type on the SHS catalyst was two methods, which were hydrothermal synthesis and steam-assisted crystallization (SAC) process. The results of both methods represented the increase of narrower hydrocarbon products, isoparaffins and olefins selectivity due to acid sites of the zeolite. However, these methods as the improved cobalt based over SHS catalyst had some problems such as the decomposing of the silica, removing of cobalt metals on the SHS support and uncovering of some zeolite over the SHS catalysts.