| Autor: |
François Fajula, R. Dutartre, D. McQueen, Lovat V.C. Rees, Philippe Schulz |
| Rok vydání: |
1994 |
| Předmět: |
|
| DOI: |
10.1016/s0167-2991(08)63676-9 |
| Popis: |
The diffusion of o-, m- and p-xylene isomers in a series of mazzite zeolites in their H + form has been studied using the frequency response technique. The mazzite samples have all been prepared by steam dealumination followed by acid leaching of two parent materials synthesised with different aluminium contents: one contains 9 Al atoms per unit cell (Si/A1 = 3) and the other 7 Al atoms per unit cell (Si/Al = 4). The dealuminated materials exhibit similar Si/Al framework ratios but contain differing amounts of extra-lattice aluminium. Analysis of the adsorption/desorption nitrogen isotherms reveals large differences in the size and volume of the mesopores created by dealumination depending on the composition of the parent zeolite. Dealumination of the aluminium rich parent sample yields mesopores 100A in diameter and whose volume amounts to 0.05-0.06 ml/g. The aluminium poor parent material generates smaller mesopores (60-80A) representing a volume of 0.03-0.04ml/g. Frequency response measurements show that the diffusion in these solids is controlled not by the amount of non-framework aluminum but by the number, volume and distribution of mesopores (created during steaming). At 373K and 1 torr, the self diffusion coefficients of p-xylene in the mazzite samples are of the order 0.7-3×10 −11 m 2 s −1 . |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
