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

Abstract

Ap hosphorous-modified Al 2 O 3 support was prepared by the impregnation methoda nd applied for the preparation of cobalt-based Fischer-Tropsch synthesis (FTS) catalysts (Co/P-Al 2 O 3 ), which were calcined at different temperatures. The Co/ P-Al 2 O 3 showed as ignificant increaseo ft hermals tability with ah igher catalytic performance without severe deactivation even above ac alcination temperature of 600 8Cc ompared with the unmodified Co/Al 2 O 3 .T hese findings are explained by the suppressed cobalt aluminate formation and less pronounced aggregation of cobaltp articles. The suppressed aggregation of cobalt particles is attributed to the localized presence of aluminump hosphate by forming at hermally stable metal-phosphorous oxo-species on Al 2 O 3 surfaces thus suppressing the migration of cobalt particles to the outer pore mouths of the support. These effects significantly enhance the catalytic activity with ah igher thermal stabilityo ft he catalysts.

Correlation of Sol–Gel Alumina‐Supported Cobalt Catalyst Processing to Cobalt Speciation, Ethanol Steam Reforming Activity, and Stability

“…In particular, alumina is an important support for cobalt catalysts used in many industrial reactions as hydrodesulfurization, Fischer–Tropsch synthesis and steam reforming of methane and ethanol . However, alumina exhibits a rather complex surface chemistry, and many studies have been conducted for establishing the effects of the alumina support properties on the cobalt catalyst performance …”

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.…”

“…[13][14][15][16][17]26] The significantly reduced surface area and pore volume as well as slightly increased average pore diameter on the fresh P/m-CoAl at a higher phosphorous content could be possibly attributed to the preferential deposition of phosphorous species on the outer surfaces of the m-CoAl, which can form the much denser SiO 2like AlPO 4 phases. [19][20][21][22][23][24] The ordered mesoporous structures of the P/m-CoAl were also verified by a small-angle X-ray scattering (SAXS) analysis, and the SAXS peaks are displayed in supplementary Figure S2. A clearly large peak intensity at 2θ = 1.23°suggests the formation of the highly ordered mesoporous structures on the fresh m-CoAl, which were well-preserved even on the phosphorous-modified P/m-CoAl.…”

“…[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.…”

Fischer–Tropsch synthesis over MOF-supported cobalt catalysts (Co@MIL-53(Al))

“…was well documented. 60 The preliminary tests revealed the effect of the activation of the MIL-53(Al) host matrix on the catalytic performance of Co-containing nanohybrids produced on its basis. It has been reported previously that the conventional calcination procedure accomplished at 330°C (72 h) did not lead to complete release of occluded benzene-1,4dicarboxylic acid from MIL-53(Al) pores.…”