Effects of calcination, metal dispersion, metal particle size, and metal-support interaction on Fischer-Tropsch activity and selectivity of different sized titanosilicate supported cobalt (15 wt.%) catalyst were studied and compared in a fixed bed reactor at 220 °C, 250 psi, 2000 h-1, and H2/CO = 2. Three titanosilicate materials (pore dia = 50(N), 90(M), 250(W) Å) were synthesized and used as support. Each catalyst was divided into two sets, one was calcined at 400 °C in static air (CA) and another was left uncalcined (UC). Both sets of catalysts were reduced in situ under 60 mL/min of H2 flow prior to the catalytic study. It was hypothesized that in situ reduction without calcination will result in higher dispersion and thus higher activity. The UC catalysts were reduced and passivated with 1 vol.% oxygen prior to XRD, BET and XANES analysis. X-ray diffractograms of the catalysts revealed that cobalt crystal sizes were a function of the pore size of the catalyst and were smaller for UC catalysts. TPR profiles revealed that the Co3O4→CoO transition was more facile in UC catalysts at nearly 35 °C lower than the CA catalysts. However, the CoO→Co transition temperature was unaffected by calcination or pore size. The activities for these catalysts are compared in Figure. CA catalysts showed higher CO conversion and C5+ selectivity. Higher Co dispersion and strong association of Ti in the support with Co may have lowered activity for UC catalysts. The narrow and medium pore catalysts remained stable up to 100 h time-on-stream whereas the wide pore catalysts exhibited gradual deactivation. Higher reducibility of cobalt particles in the medium pore catalyst and better dispersion of cobalt in the narrow pore catalyst are likely to be responsible for higher activities by these catalysts.

Influence of physico-chemical properties of titanosilicate supported cobalt catalysts with different pore sizes on Fischer–Tropsch activity

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.