Figure 6.

Combined effects of support porosity and chemical promotion on the selectivity to liquid olefins. Evolution of (a) the olefin-to-paraffin molar ratio with the carbon chain-length for C_3–10 hydrocarbon products and; (b) the olefin molar abundance within the C_5–10 liquid products with the average support pore diameter, obtained with various cobalt-based FT catalysts supported on unimodal mesoporous or multimodal meso-macroporous γ-Al₂O₃ carriers of varying pore diameters either in their unpromoted form (open symbols and dotted lines) or promoted with PrO_x (1.0 Pr_at nm²) (closed symbols and solid lines). In panel (b), catalysts to the right of the x-axis interrupt show a multimodal pore architecture with both meso- and macropores and thus no specific average pore diameter has been assigned. Reaction conditions: T = 473 K, P = 20 bar, H₂/CO = 2, WHSV = 5.5–33.0 h^–1, CO conversion = 20 ± 3%. The gray-shaded area on panel (b) illustrates the increase in olefinicity for the C_5–10 liquid FT products due to the incorporation of PrO_x as promoter.