Isothermal equilibrium hydrogen pressure measurements were carried out as a function of composition for the yttrium-hydrogen system in the temperature ranges 250 to 350" and 650 to 950", up to a pressure of 1 atm. The existence of three solid solution phases in this system is indicated by the data. The primary solid solution range extends to about YH0.55. The other two solid solution phases can be described as yttrium hydride phases deficient in hydrogen with respect to YH2 and YH3. The phase boundaries were evaluated in the temperature ranges 650 to 950" and 250 to 350", respectively. The experimental relative partial molal and integral thermodynamic quantities were calculated. IntroductionAlthough the position of yttrium metal in the periodic table is significant in regard to the correlation of the properties of the hydrogen compounds with those of the alkaline earth, transitional, and rare earth hydrides, the lack of available high-purity metal has been a hindrance to accurate work on the Y-H system.Lundin and Blackledge2 recently published pressuretemperature-composition curves for the Y-H system in the temperature range 900 to 1350". They reported the existence of a stable hydrogen-deficient yttrium dihydride in this temperature range and determined the solubility limits of hydrogen in yttrium and yttrium dihydride. They also reported the existence of YH3 from 300" down to room temperature but gave no isotherinal equilibrium pressure measurements for this low temperature range. Their findings have been substantiated also by X-ray data of Dialer and Frank.3 Flotow, Osborne, and Otto416 have also reported the preparation of YHs and YHB and the measurement of low-temperature heat capacities.The purpose of the work reported here was the determination of thermodynamic data and the elucidation of the yttrium-hydrogen phase diagram.

Extensive thermodynamic and preliminary experimental studies have identified the potential use of aluminosilicate materials to simultaneously remove volatile alkali and particulate released during pressurized gasification of coal. The gettering capacity of three selected materials have been evaluated in a bench-scale reactor operating at 1114 kPa total pressure and 1123–1173K in alkali-laden inert, and simulated fuel gas environments. At 1123 K, alkali gettering has been established to result through reaction within the amorphous acid-insoluble alumino-silicate fraction of these materials, while at 1173 K saturation of the insoluble matrix is achieved, with gettering occurring mainly through acid-soluble complexes. The gettering mechanism as either a chemical reaction or a physical adsorption phenomenon and reaction kinetics will be delineated through future thermogravimetric (TG) analyses.

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