Scaling Dimensions of Nitrogen Adsorption Characteristics in Modulated Mesoporous Aluminophosphates
✍ Scribed by Dimitris E. Petrakis; Ioannis Pasxalidis; Charis R. Theocharis; Michael J. Hudson; Philip J. Pomonis
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 159 KB
- Volume
- 185
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
N m vs log d, the values of D S can be determined. An alterna-Mesoporous alumina-aluminophosphates (MAAP) of the gentive method consists of adsorbing the same kind of molecule, eral formula Al 100 P X M 20 (M Å Al, Fe, Cr, and Ni and X Å 0, 4.5, usually N 2 , on a particular adsorbent sieved according to 9, 18, 36, 72, and 144) were tested for their pore size distribution different particle sizes d and reevaluating again N m . Then by nitrogen adsorption. The distribution of pore size can be modiplots of log N m vs log d lead easily to the D S values. fied by the addition of phosphorus. The scaling or fractal dimen-The above methods probe information at the scale range sions (D S ) of the adsorption characteristics in the pores, calculated of molecular sizes in the range 10-20 A ˚. However, in the from the plots of the log of the corresponding cumulative BJH molecular scale range 20-1000 A ˚where polymolecular addesorption pores surface area versus the log of the corresponding sorption develops, different methods have been put forward pore size, indicate that for low values of P/P 0 , the adsorption proceeds in a two-dimensional manner, independently of the pore (6-9). One such recent method dealing with the range of size distribution (p.s.d.). However, at high P/P 0 values and narrow polymolecular adsorption is the thermodynamic method prop.s.d. D S § 3, while at wide p.s.d. D S ú 3. At medium P/P 0 values posed by Neimark (10) and Neimark and Unger (11). These the D S values obtained were found as high as 10 for narrow pore authors employed a modified version of the standard Frensize distribution and decrease as the p.s.d. becomes wide by the kel-Halsey-Hill (FHH) isotherm for nitrogen adsorption addition of phosphorus. These phenomena are related to the superon a smooth surface, critical condensation of nitrogen in the pores of MAAP.