Ceramic and Metal-Composite Membranes: Synthesis, Characterization and Reaction Studies

摘要 - Varma - 9529172 无机膜在膜反应器中同时进行反应和分离的最终成功工业应用取决于生产具有所需结构、催化和渗透性能的膜的能力。 在许多具有实际意义的情况下，催化剂的最佳分布是颗粒内和膜内的多步函数。 在催化膜中，可以通过活性和惰性溶胶的连续注浆来获得活性元素的精确分布。 在这些膜中，渗透研究表明努森流具有高通量。 已经开发了合成程序来制备具有受控活性催化剂分布的选择性渗透金属复合膜和微孔膜。 已经证明，对于相同量的催化剂和活性表面积，不均匀颗粒比均匀颗粒具有更高的总转化率。 PI计划研究金属复合材料和微孔陶瓷膜。 对于金属复合膜的情况，他将确定化学镀和渗透过程中薄膜生长的机制，推导出沉积动力学，并根据实验结果开发数学模型。 合成化学和动力学将与薄膜微观结构（使用计算机模拟）和膜性能相关。 根据这些结果，将优化合成参数以产生具有所需性能的膜。 对于微孔膜，将确定合成参数（溶胶-凝胶和注浆特性）对膜材料的结构、渗透和催化性能的作用，以提供对合成过程的理解。 此外，将开发获得并维持每单位反应器体积的高催化剂表面积的方法。 最后，还将检查这些膜在实践中遇到的严酷化学和热条件下的稳定性。 这些反应和分离膜以及新型薄膜复合催化膜的性能将使用脱氢（乙烷转化为乙烯、氨分解）和部分氧化（乙烯环氧化）作为探针反应进行评估。 这项工作的成功完成将增强对合成与结构之间关系以及结构如何影响膜的材料、渗透和反应性能的基本理解。

Abstract - Varma - 9529172 The eventual successful industrial application of inorganic membranes for simultaneous reaction and separation in membrane reactors depends on the ability to produce membranes of desired structural, catalytic and permeation properties. In many cases of practical interest, the optimal distribution of catalyst is a multiple-step function within the pellet and in the membrane. In catalytic membranes, precise distribution of the active element can be obtained using sequential slip-casting of active and inert sols. In these membranes, permeation studies indicate Knudsen flow with high fluxes. Synthesis procedures have been developed to prepare permselective metal composite membranes and microporous membranes with controlled active catalyst distributions. It has been demonstrated that for the same amount of catalyst and active surface area, nonuniform pellets have a higher overall conversion than uniform pellets. The PI plans to study metal composite and microporous ceramic membranes. For the case of metal composite membranes, he will determine the mechanism of film growth during electroless plating and osmosis, derive the deposition kinetics and develop a mathematical model based on the experimental findings. The synthesis chemistry and kinetics will be correlated with the film microstructure (using computer simulation) and membrane performance. On the basis of these results, the synthesis parameters will be optimized to yield membranes of desired properties. In the case of microporous membranes, the role of synthesis parameters (sol-gel and slip-casting characteristics) on the structure, permeation and catalytic properties of membrane materials will be determined to provide an understanding of the synthesis process. Further, methods will be developed to obtain and maintain high catalyst surface area per unit reactor volume. Finally, the stability of these membranes under the severe chemical and thermal conditions encountered in practice will also be examin ed. The performance of these membranes for reaction and separation, and that of a novel thin film composite catalytic membrane, will be evaluated using dehydrogenation (ethane to ethylene, ammonia decomposition) and partial oxidation (ethylene epoxidation) as probe reactions. A successful completion of this work will enhance the fundamental understanding of the relationship between synthesis and structure, and how the structure affects the material, permeation and reaction properties of the membrane.