Effect of tetrahedral aluminum on the catalytic performance of Al–SBA-15 supported Ru catalysts in Fischer–Tropsch synthesis

Abstract

Al–SBA-15 supports were synthesized by both direct synthesis and post-synthesis grafting methods. The two synthetic methods lead to different tetrahedral Al sites; Al(x)-D samples prepared by direct synthesis exhibit more tetrahedral Al sites than Al(x)-P supports prepared by the post-synthesis grafting method as determined by ²⁷Al magic-angle-spinning NMR (²⁷Al MAS NMR). The temperature-programmed desorption of ammonia (NH₃-TPD) result shows that the material with more tetrahedral Al sites has higher acidity. The Al–SBA-15 material supported ruthenium catalysts were applied in Fischer–Tropsch synthesis (FTS). The tetrahedral Al content is shown to promote the dispersion of ruthenium in the supported catalysts, which is illustrated by powder X-ray diffraction (XRD), nitrogen adsorption–desorption and hydrogen temperature programmed desorption (H₂-TPD). The effect of tetrahedral Al on the catalytic selectivity was discussed. The selectivity of long chain hydrocarbons (C₁₁₊) is lower for the catalyst with higher content of tetrahedral Al sites in FTS.