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Keywords:

  • multibed reaction system;
  • middle distillates;
  • Fischer–Tropsch synthesis;
  • oligomerization;
  • hydrocracking/isomerization;
  • supercritical phase conditions

A vertically aligned fixed-bed reactor system with a cascade of three sequential catalyst beds has been used to incorporate Fischer–Tropsch synthesis (FTS) in the first bed, oligomerization (O) in the second bed, and hydrocracking/isomerization (HC or C) in the third bed (FTOC). Compared to gas phase FTS (GP-FT) alone, gas phase FTS with the subsequent upgrading beds (GP-FTOC) is demonstrated to result in a reduction in the olefin selectivity, a reduction in the C26+ selectivity, and a marked enhancement in the production of branched paraffins and aromatics. Utilization of supercritical hexane as the reaction medium in supercritical FTS (SC-FT) and supercritical phase FTOC (SC-FTOC) resulted in a significant reduction in both CH4 selectivity and CO2 selectivity. Interestingly, significant amounts of aldehydes and cyclo-paraffins were collected in SC-FT and in SC-FTOC, respectively, while not being observed in traditional gas phase operation (both GP-FT and GP-FTOC). © 2014 American Institute of Chemical Engineers AIChE J, 60: 2573–2583, 2014