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The reduction pathway of Co catalysts supported on untreated SiO2 along with two pretreated SiO2 support materials was investigated. In situ XRD studies clearly showed the likely reduction pathways of the cobalt oxides on the untreated SiO2, ethylene glycol pretreated SiO2, and annealing pretreated SiO2 supports. Ethylene glycol pretreated SiO2-supported Co (Co/E–SiO2) catalyst showed smaller metal crystallites, highly dispersed Co and high Co(hcp)/Co(fcc) ratio because of the high percentage of non-H-bonded silanols; however, the high percentage of the non-H-bonded silanols created a strong Co-SiO2 interaction which caused a low degree of reduction of CoO resulting in lower FT activity. In contrast, the annealing pretreated SiO2-supported Co (Co/A–SiO2) catalyst did not significantly increase the percentage of non-H-bonded silanols and Co(hcp)/Co(fcc) ratio when compared with Co/E–SiO2, but it exhibited a better catalytic activity during FTS. [ABSTRACT FROM AUTHOR]

Olefin/paraffin (C2-C6) = 1.2 (after 2 h) C1 = 25.0%. Olefin/paraffin (C2-C6) = 0.9 (after 4 h) C1 = 17.0%, C2-C4 = 28.0%, C5-C12 = 13.0%, C13-C18 = 23.0%, C19+ = 19.0%. Olefin/paraffin (C2-C6) = 0.9 (after 4 h) C1 = 22.0%, C2-C4 = 42.0%, C5-C12 = 19.0%, C13-C18 = 13.0%, C19+ = 4.0%. Olefin/paraffin (C2-C6) = - (after 2 h) C1 = 26.0%. [Extracted from the article]

Abstract: Carbon nanotubes (CNTs) were obtained through the catalytic decomposition of C2H2 at 700°C over Fe–Co supported on CaCO3 and confirmed by TEM to be composed of multiwalled carbon nanotubes. The CNTs were refluxed in 30% and 55% HNO3 for 2 and 6h in order to remove impurities and introduce oxygen surface groups. This rendered the CNTs less hydrophobic. The morphology, microstructure, surface area, pore volume and surface chemical properties of the acid treated CNTs were analysed by TEM, N2 physisorption, TGA, FTIR, Raman spectroscopy and zeta potential measurements. The surface roughness, together with the degree of surface functionalization correlated with the harshness (time and concentration) of the acid treatment. Fischer–Tropsch synthesis studies (275°C, 8bar) were performed on all the Fe loaded (10%)/CNT catalysts and activity studies revealed that the more severe the acid treatment the higher the activity of the catalysts. [ABSTRACT FROM AUTHOR]