This study was aimed at modifying the pore structure and surface chemistry of a zeolite to achieve an ideal material for gas-fired dehumidifying and cooling system application. Zeolite Y was chemically modified with various amounts of ethylenediaminetetraacetic acid (H4EDTA) corresponding to H4EDTA/Al (zeolite) molar ratio, X=0.5, 0.6, 0.75, 0.9 and 1.0 under reflux condition to achieve various degrees of dealumination. Sample treated with X=0.5 remained highly crystalline, but crystallinity of the samples decreased as the X increased. Although the sample treated with X=0.9 was x-ray amorphous, SEM micrographs indicated that the original crystal morphology was largely preserved. Chemical analysis and 29Si showed a progressive extraction of Al and Na with increased X. 27Al MASNMR indicated that AlIV was the only Al species up to X=0.75, whereas the x-ray amorphous phase (X=0.9) exhibited three peaks at 60, 52 and 38 ppm indicating the distortion of and change in AlIV coordination. Adsorption analyses using H2O, N2 or Ar as probe molecules indicated that the X-ray amorphous product remained essentially microporous having a broad micropore size distribution and a reduced hydrophilicity. Consequently, water adsorption isotherm changed from an extreme Type I to a moderate Type I. The moderate Type I isotherm with water is the key for its suitability as a desiccant in gas-fired dehumidifying and cooling system. These materials are also potentially useful in solar heating and cooling applications.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering