Studies on Salt Hydrates for Latent Heat Storage. VII. The Relation between Activation Process of Crystal Nucleation Catalysts for Sodium Acetate Trihydrate and Their Deactivation Temperatures

Influences of preheating temperature were studied on crystallization of CH3CO2Na·3H2O from its melts containing a small amount of Na4P2O7 or Na2HPO4 as a crystal nucleation catalyst. The relation between the activation process of these nucleation catalysts and their deactivation temperatures was investigated in detail. Aging of nucleation catalyst which was preceded by forced crystallization of CH3CO2Na·3H2O from its melt containing the catalyst, largely affects the catalyst’s deactivation temperature. Whenever Na4P2O7 or Na2HPO4 was used as a nucleation catalyst, the deactivation temperature was raised by lengthening aging time at a constant aging temperature. When the catalysts were aged for 4 d at 20 °C, the aging effect on them was almost saturated. At lower temperatures, longer aging times were required for saturation of the effect. The results obtained are discussed with a modified adsorption model, which takes into account commensurate-incommensurate phase transition of solid adsorbate.