Studies on the Adsorptive Behaviors of Hydrogen on Supported lridium Catalysts Using Isosteric Heat, the Elovich Equation and TEM

利用等壓吸附熱、Elovich 方程式及穿透式電子顯微鏡研究氫在銥觸媒上的吸附行為

張聰慧(Tsong-Huei Chang) ； 陳仕元(Shyh-Yuan Cheng) ； 呂芳欽(Fang-Chin Leu)

《Journal of the Chinese Institute of Chemical Engineers》 32卷1期 (2001/01) Pp. 75-80

https://doi.org/10.6967/JCICE.200101.0075

摘要

本研究中的銥觸媒係利用初期潤溼法製備，並用等壓吸附熱、穿透式電子顯微鏡及Elovich方程式來研究氫在還原態的銥觸媒上的吸附行為。研究中發現，當吸附溫度在323K (吸附溫度在273~473K)時，銥觸媒對氫的吸附量達到最大。此現象顯示氫對銥觸媒的吸附在323K以下需要活化能，其值為31~34kJmol-1。另外，研究結果也揭示，氫在還原態的銥觸媒上有兩種不同的吸附形態，可能分別吸附在銥觸媒的次表層及表層上，而它們的吸附熱分別為-65~-40kJmol-1及-20kJmol-1。

並列摘要

Supported iridium catalysts were prepared using the method of incipient wetness by impregnating various supports with a solution of iridium trichloride. The behaviors of hydrogen adsorption on the reduced catalysts were investigated by means of TEM, measurements of the adsorption isotherm in the temperature range of 273~473 K, calculation of the isosteric heat and the activation energy. The maximum capacity of hydrogen adsorption on the supported iridium catalysts appeared at the mid-temperature at 323 K instead of 273 K. This abnormal phenomenon suggested that an activated process was necessary during hydrogen adsorption on the nomenon suggested that an activated process was necessary during hydrogen adsorption on the supported iridium catalysts. The energy barrier of this activated process was calculated to be 31~34 kJ mol-1. Furthermore, two types of adsorbed hydrogen with distinct isosteric heat (-65 ~ - 40 kJ mol-1 and - 20 kJ mol-1) were found through analysis of the hydrogen adsorption isotherms using the Clausius-Clapeyron equation. These two types of adsorbed hydrogen were believed to derive from hydrogen adsorption on the subsurface layer and surface layer of the iridium crystallites, respectively.

並列關鍵字

Iridium Catalyst ； Isosteric Heat ； TEM ； Elovich Equation