氢分离与CO催化甲烷化双功能型钯复合膜

以多孔Al₂O₃陶瓷为基体材料, 采用浸渍法担载NiO后用2B铅笔修饰NiO/Al₂O₃表面, 通过化学镀法沉积约5 μm厚的金属钯, 还原后成功制得Pd/Pencil/Ni/Al₂O₃膜. 为进行对比, 还制备了未担载镍的Pd/Pencil/Al₂O₃膜. 膜的表面和断面形貌分别采用扫描电镜和金相显微镜观测, 膜的透氢动力学通过H₂/N₂单气体法测试, 并以成分为H₂ 77.8%, CO 5.2%, CO₂ 13.5%和CH₄ 3.5%的原料氢测定了膜的氢分离效果. 结果表明, 未载镍的Pd/Pencil/Al₂O₃膜只具有氢分离作用, 而Pd/Pencil/Ni/Al₂O₃膜还可以有效地将钯膜泄漏的CO和CO₂转化为甲烷, 因而成为双功能型钯膜. 这种双功能膜尤其适用于面向质子交换膜燃料电池(PEMFC)的氢气分离, 既有效解决了PEMFC对氢燃料中CO格外敏感的难题, 又提高了对钯膜缺陷的容忍度, 因而延长了钯膜的使用寿命.

Bifunctional palladium composite membrane for hydrogen separation and catalytic CO methanation

NiO was introduced into the porous Al₂O₃ substrate by impregnation, and the resulting NiO/Al₂O₃ was coated with the lead of a 2B pencil to modify its surface. A palladium layer with a thickness of 5 μm was deposited by electroless plating on the Pencil/NiO/Al₂O₃ substrate, and a Pd/Pencil/Ni/ Al₂O₃ membrane was obtained after reduction with hydrogen. For reference, a Ni-free Pd/Pencil/ Al₂O₃ membrane was also fabricated. The surface and cross-sectional morphologies of the membranes were studied by scanning electron microscopy and metallographic microscopy. The hydrogen permeation kinetics was investigated by single gas tests, and the hydrogen separation performances of the Pd/Pencil/Al₂O₃ and Pd/Pencil/NiO/Al₂O₃ membranes were tested with a hydrogen feed composed of H₂ 77.8%, CO 5.2%, CO₂ 13.5%, and CH₄ 3.5%. The Ni-free Pd/Pencil/Al₂O₃ membrane only shows function of hydrogen separation, while the Pd/Pencil/Ni/Al₂O₃ is also catalytically effective for methanation of CO and CO₂ in hydrogen, forming a bifunctional palladium membrane concept. Since the amount of CO and CO₂ in the hydrogen after membrane separation is very low, the consumption of hydrogen by the methanation reactions is negligible. The bifunctional membrane is promising for proton exchange membrane fuel cells because the catalytic methanation treatment solves the CO poisoning problem of the fuel cell electrodes and consequently allows the palladium membrane to tolerate more membrane defects and to achieve longer life.