1Research Institute of Petroleum Industry (RIPI), P.O. Box 18745-4163 Tehran, I.R. IRAN
2Department of Chemical Engineering, University of Tehran, P.O. Box 11365-4563 Tehran, I.R. IRAN
3Department of Chemical Engineering, University of Saskatchewan, Saskatoon, SK, S7N5C5, CANADA
The potential of carbon nanotubes (CNT) supported cobalt catalysts for Fischer-Tropsch (FT) reaction is shown. Using the wet impregnation method cobalt on carbon nanotubes catalysts were prepared with cobalt loading varying from 15 to 45 wt. %. The catalysts are characterized by different methods including: BET physisorption, X-ray diffraction, hydrogen chemisorption, and temperature-programmed reduction. The activity and product selectivity of the catalysts were assessed and compared with alumina supported cobalt catalysts using a continuous-stirred tank reactor (CSTR). Using carbon nanotubes as cobalt catalyst support was found to decrease the reduction temperature of Co3O4 to CoO from 440 to 347 oC and that of CoO to Coo from 640 to 574 oC. The strong metal-support interactions are reduced to a large extent and the reducibility of the catalysts improved by 67.7 %. CNT aided in well dispersion of metal clusters and average cobalt clusters size of the reduced cobalts is decreased from 5.3 to 4.9 nm. Results are presented showing that the hydrocarbon yield obtained by CNT supported cobalt catalyst is 74.6 % more than that obtained from cobalt on alumina supports. The maximum concentration of active surface Coo sites and FTS activity for CNT supported catalysts are achieved 40 wt. % cobalt loading. CNT caused a slight decrease in the FTS product distribution to lower molecular weight hydrocarbons.
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