Tuning the catalytic performance of Fischer-Tropsch synthesis by regulating the Al2O3-layer over Co/Al2O3/Al catalysts

The main requirement for Co-based catalysts in Fischer-Tropsch synthesis (FTS) is to efficiently convert syngas (H 2 +CO) into long-chain hydrocarbons (C 5+ ). Since the formation of long-chain hydrocarbons (C 5+ ) is thermodynamically favored at low temperatures, it is desirable to develop efficient catalytic systems that can allow working at a relatively low reaction temperature. Herein, the Al 2 O 3 /Al composite has been used as support for the Co-based catalysts. The catalytic performance of Co/Al 2 O 3 /Al catalysts in FTS can be regulated by varying the Al 2 O 3 -layer thickness. With the thickening of Al 2 O 3 -layer, the catalytic activity and selectivity toward C 5+  hydrocarbons over Co/Al 2 O 3 /Al decrease markedly, although the number of accessible Co 0 sites increases obviously. This Al 2 O 3 -thickness-dependent FTS performance can be attributed to a variation of the proportion of active species Co-AlO x -Al and less active species Co-Al 2 O 3 . On the basis of the above finding, a highly active catalyst (Co/Al-0) has been developed using commercial Al metal powers as support, which will enable the FTS process to work at a fairly low reaction temperature (below 185 °C) and maintain excellent catalytic activity. This study provides a practical but low-cost method to modulate the electronic properties of metal catalysts by using available metal powders.