Enhancement of performance and stability of Graphene nano sheets supported cobalt catalyst in Fischer–Tropsch synthesis using Graphene functionalization

Abstract

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. 15wt.% 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 H2chemisorption tests, 480hrs continuous FT synthesis increased the average cobalt particle size from about 7.8 to 8.8nm for Co/GNS catalyst and from about 6.8 to 7.2nm 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 480hrs 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.