ADSORPTION CHARACTERISTICS OF DICHLORODIFLUOROMETHANE (FREON-12) OVER Pd-SUPPORTED ON SiO₂ AND AlF₃ MATRICES PREPARED BY SOL-GEL METHOD

Rateb Hina and Isam Arafa
Department of Applied Chemical Sciences, Jordan University of Science & Technology,P.O. Box 3030, Irbid 22110, Jordan. Tel. 962-2-7201000/23748, Fax: 962-2-7095014, E-mail: drrhina@yahoo.com

Abstract
0.5% Pd supported on SiO₂ and AlF₃ matrices were prepared by sol-gel method. The morphology, surface porosity (BET surface area, pore volume & pore diameter) and total surface acidity of these catalysts were investigated using scanning electron microscopy (SEM), N₂ adsorption isotherm and gas-phase pyridine adsorption, respectively. It was found that the BET specific surface area and total pore volume of 0.5% Pd/SiO₂ are larger than those of 0.5% Pd/AlF₃ whereas the total surface acidity was higher in the case of 0.5% Pd/AlF₃ catalyst. The gas-phase adsorption process of dichlorodifluoromethane (freon-12) over the prepared catalysts was investigated at 0, 31, 55 and 180 °C. The fraction of sites (θ) occupied by freon-12 at these conditions, were calculated from Langmuir adsorption isotherm. Thermodynamic analysis of freon-12 adsorption data at equilibrium (K_ads, DG_ads, DH_ads and DS_ads) indicates that the adsorption of freon-12 over 0.5% Pd/AlF₃ was more favorable than that on 0.5% Pd/SiO₂.

Key words: Freon-12, Adsorption thermodynamics, Sol-gel, Pd-supported on silica and aluminumfluoride, SEM.