Sulfur resistant Pd and Pd alloy membranes by phosphidation
Sulfur resistant Pd and Pd alloy membranes by phosphidation
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DOI：
10.1016/j.memsci.2013.12.074
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发表时间：
2014-04
影响因子：
9.5
通讯作者：
S. J. Khatib;Samhun Yun;S. Oyama
中科院分区：
文献类型：
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作者：
S. J. Khatib;Samhun Yun;S. Oyama
在多孔中空纤维α-Al 2 O3载体上制备了含磷组分的新型超薄Pd和Pd合金（Pd-Ag，Pd-Cu）膜。目的是研究存在的P添加剂对膜的行为对硫中毒的影响。为了在结构中引入P，将膜暴露于作为气态磷源的PH 3。通过在暴露于100 ppm H2S/H2的气体混合物之前和期间以及在H2中再生之后测量在673 K下的氢渗透性和H2/N2选择性来评价具有和不具有P的膜的性能和耐硫性。通过X射线衍射（XRD）、X射线光电子能谱（XPS）和扫描电子显微镜（SEM）对暴露于H2S之前和暴露/再生之后的膜进行表征。XRD显示在任何暴露的或P处理的膜中分别没有可检测量的硫或磷化合物。XPS分析表明，经H_2S/H_2处理的Pd和Pd-Ag膜表面存在S。在Pd-Cu膜的表面上没有检测到S，表明在后者中没有形成不可逆的S化合物。P处理的膜的表面上也检测到P。磷的存在降低了Pd合金膜的氢渗透率和H2/N2选择性，但却显著提高了Pd合金膜对H2S中毒后H2的回收能力。Pd-Cu膜在再生后仅恢复了部分H2渗透率，从11.2×10− 7 mol m−2s− 1 Pa −1（制备时）变为2.3×10− 7 mol m−2s− 1 Pa −1，而在P存在下，H2渗透率从5.2×10− 7 mol m−2s− 1 Pa −1（制备时）变为6.5×10− 7 mol m− 2s − 1 Pa − 1，其H2/N2选择性从30，000增加到40，000。类似地，Pd-Ag膜在P的存在下从17×10− 7 mol m−2s− 1 Pa −1（如制备的）恢复到6.3×10− 7 mol m−2s− 1 Pa − 1，而在不存在P的情况下从52×10− 7 mol m− 2s − 1 Pa −1（如制备的）恢复到5.9×10− 7 mol m−2s− 1 Pa − 1。SEM图像显示，在不存在P的情况下，在暴露于H2S/H2的膜的表面上可见更多的裂纹和针孔。P的存在产生更均匀的表面和更少的偏析，通过抑制裂纹和针孔的形成而赋予膜结构完整性。
Novel ultra-thin Pd and Pd-alloy (Pd–Ag, Pd–Cu) membranes, with a phosphorus component, were prepared on a porous hollow fiber α-alumina support. The aim was to study the effect of the presence of a P additive on the behavior of the membranes towards sulfur poisoning. To incorporate P in the structure, the membranes were exposed to PH3as a gaseous phosphorous source. The performance and sulfur resistance of the membranes with and without P was evaluated by measuring the hydrogen permeance and the H2/N2selectivity at 673 K before and during exposure to a gas mixture of 100 ppm H2S in H2, and also after regeneration in H2. The membranes were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), both before exposure to H2S and after exposure/regeneration. XRD shows no detectable amounts of sulfur or phosphorus compounds in any of the exposed or P-treated membranes respectively. XPS indicates that S was located on the surface of the H2S/H2treated Pd and Pd–Ag membranes. No S was detected on the surface of the Pd–Cu membranes indicating that no irreversible S compounds were formed in the latter. P was also detected on the surface of the P-treated membranes. The presence of phosphorus lowered the hydrogen permeance and H2/N2selectivity; however it drastically improved the Pd-alloy membranes' capacity of recovery in H2after H2S poisoning. The Pd–Cu membrane recovered only part of its H2permeance after regeneration, going from 11.2×10−7mol m−2s−1Pa−1(as-prepared) to 2.3×10−7mol m−2s−1Pa−1, while in the presence of P the H2permeance varied from 5.2×10−7mol m−2s−1Pa−1(as-prepared) to 6.5×10−7mol m−2s−1Pa−1and its H2/N2selectivity increased from 30,000 to 40,000. Similarly, the Pd–Ag membrane recovered better in the presence of P going from 17×10−7mol m−2s−1Pa−1(as-prepared) to 6.3×10−7mol m−2s−1Pa−1in contrast to 52×10−7mol m−2s−1Pa−1(as-prepared) to 5.9×10−7mol m−2s−1Pa−1in the absence of P. SEM images show that in the absence of P, more cracks and pinholes are visible on the surface of the H2S/H2exposed membranes. The presence of P produces more homogeneous surfaces and less segregation, conferring a structural integrity to the membrane by suppressing the formation of cracks and pinholes.