Isosteric heat of adsorption at zero coverage for AQSOA-Z01/Z02/Z05 zeolites and water systems

摘要

This paper presents the evaluation of isosteric heats of adsorption at zero coverage for AQSOA type zeolites and water systems. The adsorption process is identified by favorable adsorptive sites with larger interaction potentials between water molecules and the molecular structure of AFI and CHA type zeolites, and a cylindrical Lennard-Jones potential model is applied to calculate the external wall potential. The isosteric heat of adsorption at zero coverage (Q(st)(0)) is calculated employing Boltzmann weighted potential with the multiple layers of zeolitestructure channel. The most favorable adsorptive sites are identified (i) at the surface of the zeolite pore for CHA type zeolite such as AQSOA-Z02 and (ii) inside the zeolite pore for AFI (type AQSOA-Z01 and Z05) zeolites. The simulated Q(st)(0) values are compared with (i) experimentally measured isosteric heat of adsorption data at low pressure regions (0-0.1 kPa) and (ii) Q(st)(0) obtained from the density functional theory (DFT). Theoretically, the maximum Q(st)(0) is found at the pore width of 7.5 angstrom for both AFI and CHA type zeolites. The maximum Q(st)(0) 50 kJ/ mol is obtained at the first layer of AFI zeolite (AQSOA-Z01 and Z05) structure.