GC–MS analysis indicated that the strongly adsorbed car-bon deposited on wax-extracted spent catalyst was mainly constituted of -olefins, n-paraffins, branchedalkanes/alkanes, 2-methyl-branched fatty aldehydes and 2-ketones. 2-Methyl-branched fatty carboxylicacids were mostly detected at high H2O pressure in the reactor. Branched alkenes/alkenes (2-methyl-alkenes/alkanes) were favored at high CO conversion.