Crucial factors for catalyst aggregation and deactivation on Co/Al2O3 in a slurry-phase Fischer–Tropsch synthesis

Stabilized ordered-mesoporous Co3O4 structures using Al pillar for the superior CO hydrogenation activity to hydrocarbons

“…The peak at 2920 cm −1 (denoted as I 2920 ) can be mainly assigned to asymmetric CH 3 stretching groups from the deposited long-chain hydrocarbons, and the peak at 2850 cm −1 (assigned to I 2850 ) can be originated from symmetric stretching of CH 2 groups of polymethylene chains attributed to the relatively short-chain hydrocarbons [54,59,60], which are hardly removable due to strong adsorption characters on the cobalt surfaces during the FTS reaction. The observed larger peak intensity of the CH 3 band (larger peak intensity at around 2920 cm −1 ) on the meso-Co 3 O 4 and Mn/meso-Co 3 O 4 after the FTS reaction suggests that stronger adsorption characters of amorphous heavier wax components by encapsulating the cobalt surfaces as reported from our previous works [24,34,61]. The peak intensity ratios of I 2920 /I 2850 , which represent the integrated area ratios of peak at 2920 cm −1 and 2850 cm −1 , were also shown in Fig.…”

Thermally Stabilized Cobalt‐Based Fischer–Tropsch Catalysts by Phosphorous Modification of Al2O3: Effect of Calcination Temperatures on Catalyst Stability

“…[1][2][3][4][5] In general,c obalt-based FTS catalysts have been known to have the advantageous characteristics of producing heavy hydrocarbons with ah ighera ctivity and al ower water gas shift activity [6] compared to ironbased FTS catalysts. [1][2][3][4][5] In general,c obalt-based FTS catalysts have been known to have the advantageous characteristics of producing heavy hydrocarbons with ah ighera ctivity and al ower water gas shift activity [6] compared to ironbased FTS catalysts.…”

“…To design efficient FTS catalysts, the optimum particles izes of active cobalt speciesw ith af acile reducibility and al ower deactivation rate should be properly adjusted by employing suitable modifiers of supports such as the commercially available Al 2 O 3 ,T iO 2 ,a nd SiO 2 . [5] The present study,b ased on our previousw orks, [5,11] focuses on identifying the methodologies for increasing the thermal stabilityo fc obalt-based FTS catalysts especially to verify the effects of calcination temperatures on the catalytic activity and stability. Therefore, proper modification of the supports has been largely investigated by employing various metal additives on the catalysts urfaces to enhancea ctive metal dispersions as well as to prevent strong metal-support interactions by maintaining the catalyst stability even after regeneration treatment under oxidation conditions for burning out depositedh ydrocarbons.…”

Ordered Mesoporous Co3O4−Al2O3Binary Metal Oxides for CO Hydrogenation to Hydrocarbons: Synergy Effects of Phosphorus Modifier for an Enhanced Catalytic Activity and Stability

“…These structural stabilities were mainly attributed to the partial formation of thermally stable spinel-type metal aluminates at an optimal molar ratio of M/Co = 0.25 (M = Al or Zr). [13][14][15][16] In addition, the synergy effects of phosphorous species on Co/Al 2 O 3 catalysts were also reported by our previous extensive works, [19][20][21][22][23] and a superior catalytic activity on the phosphorusmodified Al 2 O 3 was observed with an improved activity and stability with less aggregation of the supported cobalt nanoparticles by partially forming hydrophobic aluminum phosphate (AlPO 4 ) species, [19][20][21] The partially formed AlPO 4 phases on the outermost γ-Al 2 O 3 surfaces inhibited the transformation of cobalt oxides to inactive cobalt aluminates due to its SiO 2 -like tridymite hydrophobic AlPO 4 surface natures by altering metal-support interactions through a stronger affinity between Al and P species than that of Al and Co species. [24] Those AlPO 4 phases can also effectively prevent the re-oxidation and aggregation of the supported cobalt nanoparticles by minimizing the phase transformations of γ-alumina to brittle boehmite (AlOOH) phase as well.…”

“…[20,21] The advantages of phosphorus incorporation on the Co/Al 2 O 3 were also reported to increase the thermal stability of active metallic cobalt nanoparticles by adjusting metalsupport interactions through a possible formation of the thermally stable spinel-type CoAl 2 O 4 phases and by enhancing the reducibility of cobalt oxide nanoparticles. [19][20][21][22][23][24] In the present study, the effects of phosphorus-modified highly ordered mesoporous Co 3 O 4 À Al 2 O 3 binary metal oxides (P/m-CoAl) during FTS reaction were investigated in terms of their structural durability [13][14][15][16][17][18]25] and outermost surface property changes to explain different catalytic activity and stability, which were not precisely reported till now as far as we know. The synergy effects of an optimal phosphorous content on the P/m-CoAl were explained by elucidating the possible phase transformations of cobalt and aluminum species as well as their positive contributions to the robust structural stability of the ordered mesoporous Co 3 O 4 À Al 2 O 3 metal oxide structures.…”