(558o) The Effect of Silanol Groups on Silica-Supported Cobalt Catalysts in Fischer-Tropsch Synthesis.

This paper focuses on the effect of the H bonded and non-H bonded (isolated) silanol groups on SiO₂-supported Co catalysts in Fischer-Tropsch synthesis (FTS). The SiO₂ supports were pretreated in order to increase the isolated SiOH on the surface of the silica. This is done to achieve a better metal dispersion and smaller metal crystallites on the surface of the SiO₂. SiO₂ supports with two different pore sizes designated as SiO₂(1) and SiO₂(2) respectively were each pre-treated in two different ways: (a) pre-treatment by thermal method (HT); (b) pre-treatment by ethylene glycol (EG). Incipient wetness impregnation was used to load 10 wt% Co on each of the six (6) supports designated as Co/SiO₂(1)UT, Co/SiO₂(2)UT, Co/SiO₂(1)HT, Co/SiO₂(2)HT, Co/SiO₂(1)EG and Co/SiO₂(2)EG. Untreated SiO₂ supported cobalt catalysts, Co/SiO₂(1)UT and Co/SiO₂(2)UT are used as a reference for this study.

In this work, various catalyst characterization techniques were used i.e. BET, XRD, Fourier-Transform Infra-red (FTIR) spectroscopy, H₂ chemisorption, temperature programmed reduction (TPR), CO temperature programmed desorption (TPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and temperature programmed surface reaction (TPSR). H₂ chemisorption, TEM and XRD results showed that the ethylene glycol pre-treated SiO₂-supported Co catalysts gave smaller metal crystallites and a better cobalt metal dispersion while TPR, CO TPD, and TPSR results indicated that these two catalysts exhibited more metal-support interaction compared to the other catalysts. FT experiment showed that thermally pre-treated SiO₂-supported Co catalysts showed better FT activity while the ethylene glycol pre-treated SiO₂-supported Co catalysts had better catalytic stability. The results of the FT experiment was in agreement with the prediction made with the TPSR studies previously done.