3 years ago

Pore enlargement of carbonaceous materials by metal oxide catalysts in the presence of steam: Influence of metal oxide size and porosity of starting material

Pore enlargement of carbonaceous materials by metal oxide catalysts in the presence of steam: Influence of metal oxide size and porosity of starting material
Porous carbon materials are produced in large amounts but are generally microporous and, thus, may have diffusion limitations for reactions with larger molecules. In this study, iron, lanthanum, cerium, nickel and cobalt oxides were studied as catalysts to enlarge or create mesopores in carbonaceous materials through metal-catalyzed steam activation. The carbonaceous materials were impregnated with 25 wt% metal nitrate salts and exposed to humidified N2 (steam, 50 cm3/min N2 plus 5 cm3/h liquid water) at 1073 K. The metal precursors were converted to metal oxides, and produced carbon samples with pore sizes between 2 and 60 nm and mesopore volumes up to 0.65 cm3/g. The size of the pores created was determined by the metal oxide size. Cobalt oxide produced the largest pores followed by nickel, cerium, lanthanum and iron oxide. For materials with mainly micropores, activation proceeded by gasification and collapse of pore walls, while for materials with larger pores, pore widening occurred. Catalyst recycling was achieved by acid leaching after activation, and no differences in the produced materials were found using fresh or recovered cerium nitrate.

Publisher URL: www.sciencedirect.com/science

DOI: S1387181117305371

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