Pd-Nb-聚倍半硅氧烷的协同作用机制对有机无机杂化微孔SiO2膜性能影响的基础研究

To fabricate microporous silica-based membranes providing with high H2 permeability and sufficient high H2/CO2 permselectivity,especially with excellent hydrothermal stability, is one of the bottle necks for implementation of ceramic microporous membranes in steam reforming and water gas shift reactions. Herein, we proposed a promising Pd-Nb doped hybrid silica membrane, as palladium and niobium are to be introduced into the bridged polysilsesquioxane networks through sol-gel approach by using hydrophobic bridged silsesquioxane,niobium pent(n)butoxide and PdCl2 as precursors. The hydrophobic -Si-CH2-CH2-Si- host structures will render the membrane a high hydrothermal stability.While the H2 permeance of the membrane can be enhanced via the palladium dopant, which can facilitate the hydrogen transportation. Simutaneously, much lower CO2 permeance of the membrane is possible due to the strong acid sites presented in membrane surface centers, which are generated by the niobium dopant.Effects of the status of palladium and niobium presented in the membrane, together with that interactions with the bridged polysilsesquioxane networks, on performances of microporous hybrid silica membranes, will be investigated in detail. The objective of this proposal is to construct a promising Pd-Nb doped hybrid silica microporous membrane, which will exhibit integrated properties of hydrogen permeability, carbon dioxide selectivity and hydrothermal stability. The above-mentioned investigations will open a new way to design microporous membranes that providing integrated high performances. More important, it is the fundamental research for ceramic membrane reactors that can be applied in main streams of the petro-chemical processes.

构筑具有高H2渗透性能和H2/CO2分离选择性，以及优异水热稳定性的微孔SiO2膜材料，是实现微孔陶瓷膜反应器用于甲烷水蒸气重整和水煤气变换反应的瓶颈和难点之一。本项目以疏水性倍半硅氧烷、五正丁氧基铌和PdCl2为前驱体，通过溶胶凝胶法将钯和铌同时引入有机无机杂化SiO2膜微结构中。利用膜微结构中疏水的-Si-CH2-CH2-Si-主体网络骨架提高膜的水热稳定性；并在膜孔筛分机理的基础上，借助Pd的选择透氢机理和Nb的强酸性，实现膜H2渗透性能和H2/CO2分离选择性的同时提高。通过Pd、Nb存在状态以及与聚倍半硅氧烷网络键合方式对微孔膜性能影响的研究，构建出H2渗透性，CO2选择性和水热稳定性三者相统一的Pd-Nb掺杂的有机无机杂化SiO2膜材料。不但为解决目前SiO2微孔膜研究中三项性能难以同时提高这一关键问题提供了新思路，而且可以奠定微孔膜反应器应用于石油化工主流程中的膜材料基础。

本项目以疏水性倍半硅氧烷（BTESE）、五正丁氧基铌和PdCl2为前驱体，通过溶胶凝胶法将钯和铌引入有机无机杂化SiO2膜微结构中以同时提高膜材料的分离性能和水热稳定性。详细研究了未掺杂、Nb掺杂、Pd掺杂和Pd-Nb二元掺杂的有机无机杂化SiO2四个体系的溶胶-凝胶过程，确定了适宜涂膜的溶胶制备条件，制备出了完整无缺陷的微孔气体分离膜，揭示了Pd、Nb掺杂对有机无机杂化SiO2膜的分离性能、水热稳定性能的影响。本项目制备出的有机无机杂化SiO2膜对H2的渗透率为2.9×10-7 mol·m-2·s-1·Pa-1，对H2/CO2的理想分离因子达到9.5；Nb掺杂的有机无机杂化SiO2膜对H2/CO2的理想分离因子高达23，但H2渗透性能较低（8.36×10-8 mol·m-2·s-1·Pa-1）；在水蒸气氛围下烧成的Pd掺杂的有机无机杂化SiO2膜不仅具有很好的H2筛分性能（H2渗透率为2.5×10-7 mol·m-2·s-1·Pa-1，H2/CO2理想分离因子为9.2），在水蒸气环境中还表现出优异的稳定性（在100 kPa水蒸气环境中H2，CO2渗透率基本维持不变，稳定时间长达190 h）；Pd-Nb掺杂的有机无机杂化SiO2膜的H2渗透率为1.5×10-7 mol·m-2·s-1·Pa-1，H2/CO2理想分离因子为18.1，分离H2和CO2混合气（H2体积浓度为50%）时，分离因子高达218，表明在Pd-Nb协同作用下，膜的H2/CO2分离性能得到了显著的提高。通过4年研究，本项目获得了具有优异的筛分性能和水热稳定性能的膜材料，为微孔膜反应器在石油化工领域的应用提供了新的可选材料；项目组共发表学术论文14篇，其中SCI收录12篇，申请专利8项，其中授权2项，培养研究生13名，获教育部技术发明奖二等奖1项。