Graphene nano sheets (GNS) were functionalized and used as cobalt Fischer-Tropsch synthesis (FTS) catalyst support. The effects of nitrogen functional groups on graphene surface on the activity, selectivity and stability of cobalt catalyst in FTS was investigated using a fixed bed micro-reactor. 15 wt.% of cobalt was loaded on the supports by impregnation method. Physico-chemical properties of pure and functionalized graphene, calcined fresh and used catalysts were studied by Raman spectroscopy, FTIR, BET, XRD, TEM, TPR and H2chemisorption techniques. According to the TEM and H(2)chemisorption tests, 480 hrs continuous FT synthesis increased the average cobalt particle size from about 7.8 to 8.8 nm for Co/GNS catalyst and from about 6.8 to 7.2 nm for Co/N-GNS catalyst. The proposed cobalt catalyst supported on functionalized GNS increased the initial %CO conversion from 70.6 to 74.5. The CO conversion over the Co/N-GNS after 480 hrs on stream decreased by 4.3% and that for Co/GNS decreased by 6.2%. For the Co/N-GNS catalyst 0.6% of total activity loss and for the Co/GNS catalyst 3.1% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step.Catalysts supported on functionalized GNS showed better stability. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.