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

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The main requirement for Co-based catalysts in Fischer-Tropsch synthesis (FTS) is to efficiently convert syngas (H2+CO) into long-chain hydrocarbons (C5+). Since the formation of long-chain hydrocarbons (C5+) 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 Al2O3/Al composite has been used as support for the Co-based catalysts. The catalytic performance of Co/Al2O3/Al catalysts in FTS can be regulated by varying the Al2O3-layer thickness. With the thickening of Al2O3-layer, the catalytic activity and selectivity toward C5+ hydrocarbons over Co/Al2O3/Al decrease markedly, although the number of accessible Co0 sites increases obviously. This Al2O3-thickness-dependent FTS performance can be attributed to a variation of the proportion of active species Co-AlOx-Al and less active species Co-Al2O3. 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.