用于甲烷高效脱氢芳构化的氢-氧/水(蒸汽)共透陶瓷中空纤维催化膜与膜反应器研究

Non-oxidative methane dehydroaromatization (MDA: 6CH4C6H6+9H2) is an important route to directly convert methane into highly valuable liquid fuels and chemicals. Its industrial application is restricted by the low thermodynamic equilibrium conversion and the fast catalyst deactivation due to carbonization reactions. In this project, we will develop a novel H2-O2/steam co-permeable ceramic hollow fiber catalytic membrane and membrane reactor for MDA, with which the thermodynamic equilibrium limitation can be broken through by H2 removal, leading to improved aromatic yields, while the stability can be improve by restraining the carbonization reactions due to oxygen/steam permeation. The details of the research include: 1) to fabricate ceramic membrane materials with high combined proton and oxygen ionic conductivity through multi-cationic doping and compounding methods,where the relationship between the composition and the ionic conduction properties will be investigated; 2) to fabricate asymmetric hollow fiber membranes composing of dense and porous layers using a modified phase inversion-sintering technique, where the formation mechanism of membrane microstructure will be detailed for optimization of the H2/O2-H2O permeability; 3) to fabricate multi-functional catalytic membranes by impregnation of Mo/ZSM-5 catalysts in the porous structure of the asymmetric hollow fiber membranes, where the membrane catalytic mechanism of MDA will be investigated; 4) to design and fabricate hollow fiber catalytic membrane reactor for MDA, with which the operating behaviors will be investigated by modeling and experiments. Through completing this project, the relation of the composition and structure of the membranes to their properties will be elucidated, and the key techniques will be grasped to fabricate the high performance membranes and membrrane reactor for MDA reaction. The study will hopefully provide both theoretical and technical supports for the industrilization of MDA process.

甲烷脱氢芳构化(MDA: 6CH4=C6H6+9H2)是天然气直接转化液体燃料和化学品的重要途径，其实际应用受热力学平衡转化率低、催化剂快速结碳失活限制。本项目研究开发一种能同时透氢-透氧/水(蒸汽)的陶瓷多功能催化膜和膜反应器，通过H2分离突破热力学平衡限制、提高芳烃产率，同时利用膜的透氧/水特性抑制积碳反应、提高稳定性。首先通过多元掺杂及材料复配制备氢-氧离子及电子混合传导陶瓷膜材料，研究材料组成与性能关系；应用改进相转化技术制备非对称陶瓷中空纤维膜，研究膜微结构控制及氢-氧/水渗透机理；浸渍负载MDA催化剂制备催化膜，研究催化膜构成与表界面特性及MDA膜催化机理；设计中空纤维催化膜反应器，研究MDA反应行为规律。通过本项目研究，阐明氢-氧/水蒸汽共透陶瓷多功能催化膜组成-结构-性能间的关系，掌握制备高性能MDA催化膜和膜反应器关键技术，为MDA工业应用提供理论和技术支撑。

甲烷作为一种重要的碳基能源分子，其高效转化利用对于优化能源结构、减少环境污染具有重要意义。甲烷脱氢芳构化是天然气直接转化液体燃料和化学品的重要途径，其实际应用受热力学平衡转化率低、催化剂快速结碳失活限制。本项目研究开发一种能同时透氢-透氧/水(蒸汽)的陶瓷多功能催化膜和膜反应器，通过H2分离突破反应热力学平衡限制、提高芳烃产率，同时利用膜的透氧/水特性抑制积碳反应、提高稳定性。.项目采用相转化和烧结技术制备了Fe和Sc共掺杂的BaCeO3（BaCe0.7Fe0.3-xScxO3-δ，BCFSc）基钙钛矿陶瓷中空纤维透氢-透氧膜，系统研究了BCFS材料组成对中空纤维膜性能的影响。通过Sc掺杂显著提高膜的热稳定性及化学和机械稳定性，但降低了膜的电导率。通过添加1.0 wt%Co2O3作为烧结助剂，可将BCFSc20（x=0.20）中空纤维膜的烧结温度降低至1400℃，该膜的H2和O2通量在1000℃时可分别达到0.32 mL min-1 cm-2和0.20 mL min-1 cm-2，而同时存在氢和氧渗透时，H2和O2通量可分别提高135%和75%，并有很好的稳定性。提出了H2和O2同时渗透的相互促进作用机理。此外，研究了BCFSc20 中空纤维膜水(蒸汽)渗透性能，在600-1000℃，水蒸气通量达到0.032-0.065 mL min-1 cm-2，外加电压对BCFS中空纤维膜的透水(蒸汽)性能有重要影响。基于Poisson-Nernst-Planck方程建立了BaCeO3基钙钛矿陶瓷膜水渗透的瞬态模型，利用模型计算了膜的透水(蒸汽)性能。.应用BCFSc20 中空纤维膜设计中空纤维膜反应器进行甲烷催化脱氢芳构化研究，实验结果表明可以明显延缓催化剂的积炭失活速率，提高产物苯的选择性和产率，在750℃时，膜反应器单独氢渗透和氢氧对向共渗透条件下苯的产率较固定床反应器分别平均提高1.25%和1.46%，在9h的反应时间内积炭平均减少10%-20%。但鉴于BCFSc膜在甲烷脱氢芳构化反应时的氢-氧通量较低，没有达到更理想的结果。为提高反应透氢速率，开发了新型金属镍中空纤维膜，用于脱氢和加氢反应，显示了很好的应用前景。通过集束可显著提高陶瓷中空纤维膜机械强度及渗透性能，克服了膜反应器组装困难的问题。