Periodic charge equilibration (PQEq) is used to study a few of the roles that the zeolite Y lattice might play in cracking catalysis. Comparison of the partial charge distributions of HY and Na 1 HY suggests that atoms within 10 Å of the sodium atom accept electrons from the sodium atom. The charge distributions of n-octane, benzene, and water adsorbed inside the supercage of zeolite Y and siliceous zeolite Y show that the lattice provides little perturbation to these molecules. In contrast, a local dipole in the zeolite Y lattice is found to induce a change in the partial charge distribution of a cracking hydride transfer transition state model (C 4 H 9 + plus n-octane). The polarization in this transition state model is attributed to the increased size of the transitionstate model in comparision to the size of n-octane. This polarization likely preferentially stabilizes species such as the transition state and is perhaps an explanation for the second-order dependence of hydrocarbon cracking rate on Al ion concentration in zeolite Y.
Abstract-A nominal 10.5-kW (3-ton) open-cycle liquid desiccant d ehumidification system has been design_ ed, installed, and successfully operated at the Solar Energy Applications Laboratory, Colorado State Umvers1ty. Packed bed units were used to dry the air in the dehumidifier and to concentrate the desiccant _m the regenerator. Liquid distribution in the regenerator was studied for two systems: a gravity tray d1stnbutor, and a spray nozzle system. Higher capacities ( 40-50% mcrease) and . lower pressure drop ( 30-40% reduction ) for the air flow were observed with the spray system. Coohng capacities of 3.5-14.0 kW ( 1.0-4.0 refngerat10n tons ) were achieved for both the regenerator and dehumidifier. Funct10nal relat1onsh1ps correlatmg.the independent variables to the rate of vaporization in the regenerator and rate of condensation m the dehum1~fier were obtained by statistical analysis of the experimental data. These studies thus proVJ~e data and .correlations useful for design guidance and performance analysis of similar open-cycle hqu1d desiccant coohng systems, particularly for the liquid / vapor contact units.
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