Isopiestic Kinetics of Pd/C/DPB Composite: Temperature Dependence

Dinh, L N ; Meulenberg, R ; Saab, A P

关键词: ACTIVATION ENERGY;    AGING;    CAPACITY;    CATALYSTS;    DIFFUSION;    GETTERS;    HYDROGEN;    KINETICS;    LIFETIME;    PELLETS;    REACTION KINETICS;    TEMPERATURE DEPENDENCE;   

DOI  :  10.2172/956833
RP-ID  :  LLNL-TR-413498
PID  :  OSTI ID: 956833
Others  :  TRN: US201014%%1685

美国|英语

来源: SciTech Connect

【 摘 要 】

In 2007, a continuation of experiments studying the uptake kinetics of a DPB getter material was conducted. In these experiments, a powder formed from ground pellets of DPB getter as currently deployed was subject to multiple hydrogenations in an isopiestic hydrogen reactor. The objective was to observe the reaction kinetics of the powdered material as a function of ambient hydrogen pressure at room temperature, with the intention of resolving key issues of the DPB reaction mechanism that could relate to its aging and capacity characteristics. The results indicated, in agreement with work performed in 2006 as part of the same project, that the likely mechanism of DPB/Hydrogen reaction occurs via the diffusion of unreacted DPB toward the catalyst surface. They also demonstrated that at a sufficiently high pressure (on the order of a few torr) of hydrogen, the reaction was vigorous enough to release sufficient heat to vaporize both the DPB getter and its hydrogenate away from the surface of the Pd catalyst at which the reaction takes place. The consequence was a premature slowing of the reaction kinetics and a drop in overall capacity. In the present work, the isopiestic reaction scheme is expanded to study the dependence of the reaction rate of this material on both hydrogen pressure and temperature. The dependence of the reaction rate on both temperature and pressure can provide both valuable clues about the reaction mechanism, as well as the activation energy of the principal reaction. The activation energy is an especially important term for purposes of doing lifetime predictions for getters under conditions of varying temperature.