Heat of Immersion and the Surface Properties of Zeolite and Magnesia

Abstract

The heat of immersion of Zeolite (Molecular Sieve-13X) in water was experimentally found to increase with its degassing temperature and to have a maximum peak at about 300°C. The acidity of Zeolite measured by n-butylamine titration also showed a similar peak at 300°C. But the heat of immersion of Zeolite in benzene showed a definite value above 200°C. It was found that though physically absorbed water or structral water may be remove at lower degassing temperature, further desorption of water and surface changes occurred above 300°C.Magnesia showed a higher heat of immersion when ground in the atmospheres of dry air and carbon dioxide. The activation of the Magnesia surface was mainly caused by the distorted surface layer, i. e., the plastic flow of the surface. From the infra-red spectra, carbon dioxide was detected on the Magnesia surfaces which were ground in the atmosphere of carbon dioxide. In this case, the surface activation by grinding was caused by the formation of an electro-static field by the chemisorbed carbon dioxide, as well as by the distortion of the surface layer.