I was synthesized an γ-alumina aerogel sample and used as a support of catalyst. The results of the BET Surface Area and Porosity Measurement before and after the addition of the active agent (15% Co, drying and calcination at 100 and 350 ˚C respectively) that made me confused. Which isotherm type (II, III or IV) is a represent of alumina aerogel sample? Did you think, the synthesize aerogel was actually a macroporous sample which was converted to a mesoporous sample after impregnation (decrease in pore diameter due adding active agent)?
I attached all of BET data for samples from before and after impregnation
Which was the precursor for the Co, nitrate? It is very unlikely that the addition of 15% Co will change this much the isotherms. Did you tried to treat the aerogel with the same drying and calcination conditions, but without any cobalt precursor?
Let me get straight, you have an aerogel, first macroporous isotherm. Then you add Co precursor, and calcinate at 350 ºC, right, leading you to a mesoporous material (but with a lack of macropores, as there is evidence of the condensation at P/P0 > 0,98.
Try calcinating the first material at 350 ºC as well, but without adding the Co precursor. To me it's a normal behavior for partial sintering at low temperature, not an effect of convertion by pore "filling" by the precursor.
Danghyan Vardan
Aerogel was first made and calcined in the air at 500 ◦C then impregnated with cobalt nitrate salt and calcined in the N2 at 350 ◦C
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