溶胶凝胶改性的钯膜表面抗硫涂层的制备及其抗硫性能研究

Pd composite membranes receive widespread attention from both academia and industry as they show great potential in the important field of hydrogen production and separation. However, the H2 permeance of Pd composite membranes can rapidly decrease in the presence of limited amount of H2S within industrial gases which appears as one of the critical issues for their commercial applications. Currently major efforts are dedicated to the formation of Pd alloys in order to improve the sulfur resistance of Pd composite membranes, which however has not seen significant progress yet. In this study, a novel approach via coating of a protective layer containing Pd nanocrystals/MoS2/alumina sol-gel particles on Pd membrane surface is proposed, which appears as a sulfur-resistant “ARMOR” . The combination of Pd nanocrystals and MoS2 particles can protect Pd membrane surface from the poisoning effect of H2S through preferential adsorption and decomposition of H2S, resulting from the high surface-to-volume ratio and strong activity of Pd nanocrystals and MoS2 particles. The sulfur-resistant “ARMOR” will be prepared by sol-gel modified suspended particles sintering method recently invented by the applicant, where the sol-gel particles can remarkably improve the adhesion and homogeneity of distribution of Pd nanocrystals and MoS2 particles. In addition, the pore size of “ARMOR” will be controlled within 0.05-0.1 µm by tuning the size of alumina sol-gel particles, Pd nanocrystals as well as MoS2 particles, which thus will not affect the hydrogen permeance of Pd membranes. This novel approach of sulfur-resistant “ARMOR” is promising to solve the problem of sulfur sensitivity for Pd composite membranes, which has an important significance for the development of novel H2 separation and purification technology at low cost.

钯复合膜在氢气分离和纯化领域有着巨大的市场前景，影响其工业应用的关键问题之一是少量H2S的存在能显著降低钯膜的透氢量。目前文献研究中最主要的抗硫方式是形成钯合金，但仍未取得明显进展。为此，本课题提出钯膜“铠甲层”抗硫新模式，即在钯膜表面涂覆纳米钯/MoS2/氧化铝溶胶凝胶修饰层，借助于纳米钯和MoS2颗粒的高比表面积和高活性优先吸附和分解H2S，进而有效保护钯膜表面。本课题将采用申请人发明的溶胶凝胶与悬浮粒子烧结相结合的方法制备“铠甲层”，氧化铝溶胶粒子将能显著提高纳米钯/MoS2颗粒间结合力和分散均匀性。另外，通过控制粒子大小，保证“铠甲层”孔径分布在0.05-0.1 µm 左右，从而不影响钯膜的透氢量。本课题对于解决钯复合膜抗硫的难题，进而开发廉价的氢气分离和纯化新工艺与新技术有重要的研究意义。

钯复合膜在超纯氢气纯化及燃料电池氢源等领域具有显著的应用前景。但是，钯复合膜化学稳定性问题一直是制约其商业化应用的主要障碍之一。比如浓度为ppm级H2S气体通过在钯复合膜表面竞争吸附或与金属钯发生化学反应生成金属硫化物，严重影响膜管透氢性能，甚至导致膜结构破坏。针对目前钯复合膜抗硫的难题，本论文提出了钯膜表面涂覆MoS2/γ-Al2O3或分子筛保护层的新方法，通过优先吸附及分解H2S避免H2S与钯膜表面直接接触，研究了两种涂层的制备及不同温度、浓度条件下的抗硫效果。.采用浸渍法在钯膜表面涂覆MoS2/γ-Al2O3保护层（厚度约6-7 μm），考察了在673 K及10-20 ppm H2S气氛下的抗硫性能，发现在40-140 h实验过程中膜管透氢及透氮速率基本保持不变。相对而言，不带涂层的纯钯复合膜在673 K和10 ppm H2S气氛下很短时间内（< 10 h）被毒化，在表面形成Pd4S，导致钯复合膜结构组成发生变化，失去氢气选择性。.采用水热合成法在钯膜表面涂覆KA与NaA分子筛（厚度约1 μm），考察了673-773 K及5-20 ppm H2S气氛下的抗硫性能，测试前后透氮性能保持不变。其中，涂覆NaA分子筛的钯复合膜在10 ppm H2S气氛下实现稳定运行1000 h。钯膜表面局部能检测到硫元素，可能是由于分子筛涂层的缺陷造成。.跟钯合金膜抗硫方案相比，涂覆 MoS2或分子筛的钯复合膜制备过程更简单，而且在长期H2S气氛测试过程中，H2和N2渗透速率都能够保持长期稳定，具有更好的耐久性。