关键词: Fischer-Tropsch synthesis, cobalt, ruthenium, microemulsion, particle size

Abstract: Bimetallic cobalt-ruthenium nano catalysts supported on carbon nanotubes (CNTs) are prepared using microemultion technique with water-to-surfactant ratios of 0.5-1.5. The nano catalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis (FTS) have been assessed in a fixed-bed microreactor. The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method. Very narrow particle size distribution has been produced by the microemulsion technique at relatively high loadings of active metals (15 wt% Co and 1 wt% Ru). According to TEM images, small Co particles (2-7 nm) were mostly confined inside the CNTs. Comparing with the catalyst prepared by impregnation, the use of microemulsion technique with water to surfactant ratio of 0.5 decreased the average cobalt oxide particle size to 4.8 nm, the dispersion was almost doubled and the reduction increased by 28%. Activity and selectivity were found to be dependent on the catalyst preparation method and water-to-surfactant ratio (as well as cobalt particle sizes). CO conversion increased from 59.1% to 75.1% and the FTS rate increased from 0.291 to 0.372 g_HC/(g_cat·h). C₅₊ liquid hydrocarbons selectivity decreased from 92.4% to 87.6%.

Key words: Fischer-Tropsch synthesis, cobalt, ruthenium, microemulsion, particle size