EAGER: LbL Polymer Thin Films for Reaction-Assisted Acid Gas Removal

1202447-Wilhite用于反应辅助分离的单一复合膜。氢气可以通过几乎任何碳氢化合物资源的催化重整来生产，已经成为一种有前途的全球能源货币。然而，目前还没有完美的解决方案来减少氢气生产中不受欢迎的副产品(如CO、CO2)--因此，这是一个巨大的挑战。我们提出了一种同时提纯H2、破坏CO和分离CO2的复合膜，该复合膜由用于选择性脱除CO2的逐层组装的聚合物薄膜和用于通过水-气变换反应将CO转化为CO2的无机催化膜组成。由此产生的复合催化-渗透选择膜代表了一种独特的、变革性的氢气净化方法，它将构建渗透选择性聚合物膜的逐层组装技术与洗涤涂层方法相结合，以构建催化膜，从而在单个复合膜中实现反应辅助气体分离。以氢为燃料的质子交换膜燃料电池(PEMFC)由于其耐用性、便携性和/或可扩展性，是下一代电力系统的主要候选者。然而，制氢过程中产生的副产物，如CO，会毒害PEMFC，严重限制其使用寿命和性能；另一种副产物CO2会稀释氢气，必须在终点使用前将其去除。目前降低CO水平的策略包括将平衡受限的水-气变换催化剂(WGS)与钯为基础的氢渗透选择膜偶联。由于钯的成本和低氢渗透性，用替代材料取代钯被视为实现经济高效的高纯氢的巨大挑战。在拟议的工作中，LBL膜可能会与钯竞争，甚至超过钯。最近在可逆选择性聚合物膜方面的研究表明，选择聚合物(即聚环氧乙烷(PEO)和聚烯丙基胺(PAH))在分离二氧化碳和氢气方面非常经济有效。建议的含有PAH的LBL薄膜与WGS催化剂一起破坏CO，可能会以低成本从含有不希望看到的副产品的重整氢流中生产高纯度、高压氢气。这项探索性拨款将探索LBL膜用于渗透选择性气体分离，其与重整化学和催化薄膜沉积技术的兼容性，最终目标是展示一种能够在典型(100-180℃)反应温度下从重整混合物中渗透选择性脱除二氧化碳的原型催化-渗透选择性膜。这项拟议的研究风险很高，因为到目前为止，所有三个中心假设都没有得到检验。LBL组件中的气体传输相对来说还没有被探索，部分原因是LBL组件和气体分离领域几乎没有交叉。到目前为止，LBL沉积技术与催化洗涤方法的兼容性尚未在文献中进行探索。最后，LBL薄膜的耐久性和性能还没有在反应环境或高温下进行研究。关于这些假设的科学结果对分居界具有实质性的学术价值。在复合催化-渗透选择膜中将催化膜和LBL聚合物膜耦合的建议得到验证，这将使我们能够严格开发一种创新的方法，实现低成本、高选择性的气体分离膜。对于水-气变换催化层提高CO2选择性LBL膜的渗透选择性的特殊情况，Wilhite最近的理论预测表明，H2-CO的渗透选择性超过250：1(与Pd膜相当)，成本可能达到大约1/100。这一成果本身就可以改变氢净化膜领域的面貌。计划的外展活动包括通过化学工程系的REU计划和工程学者计划指导本科生研究人员。PIS还将通过TAMU的国际学者计划主办一次国际研究实习。通过工程学院的RET计划，K-12教师也将获得暑期研究机会。

1202447-WilhiteSingle composite membrane for reaction-assisted separations. Hydrogen, which can be produced via catalytic reforming of virtually any hydrocarbon resource, has emerged as a promising global energy currency. However, no elegant solution for mitigating the undesired by-products of hydrogen production (e.g., CO, CO2) currently exists- thus, presenting a grand challenge. We propose to simultaneously purify H2, destroy CO and isolate CO2 using a single composite membrane comprised of a layer-by-layer (LbL) assembled polymeric thin film for selective removal of CO2 and an inorganic catalytic membrane for converting CO to CO2 via water-gas-shift reaction. The resulting composite catalytic-permselective membranes represent a unique and transformative approach to hydrogen purification by integrating layer-by-layer assembly techniques for constructing permselective polymer films with washcoating methods to construct catalytic films to achieve reaction-assisted gas separations in a single composite membrane. Proton-exchange membrane fuel cells (PEMFCs), which use hydrogen as a fuel, are a leading candidate for next-generation power systems, owing to their durability, portability and/or scalability. However, by-products from hydrogen production such as CO can poison the PEMFC and dramatically limit lifetime and performance; CO2, another by-product, dilutes the hydrogen stream and must be removed prior to endpoint usage. Current strategies for reducing CO-levels involve coupling of the equilibrium-limited water-gas-shift catalysts (WGS) with palladium-based hydrogen-permselective membranes. Because of palladium's cost and low hydrogen permeability, replacing palladium with alternative materials is viewed as a grand challenge in realizing cost-effective high-purity hydrogen. In the proposed work the LbL membranes may compete with or even surpass palladium. Recent work in reverseselective polymeric membranes indicates that select polymers (i.e., poly(ethylene oxide) (PEO) and poly(allylamine) (PAH)) are very cost-effective at separating CO2 from H2. The proposed LbL thin films containing PAH, coupled with WGS catalyst to destroy CO, may potentially produce high-purity, high-pressure hydrogen from hydrogen reformate streams containing undesired by-products at low cost. This exploratory grant will explore the use of LbL membranes for permselective gas separation, their compatibility with reforming chemistries and with catalytic thin-film deposition techniques, with the ultimate goal of demonstrating a prototype composite catalytic-permselective membrane capable of permselective CO2 removal from reformate mixtures at typical (100 - 180C) reaction temperatures. The proposed research is high-risk, as all three central hypotheses are untested to-date. Gas transfer in LbL assemblies is relatively unexplored, partly because there is little crossover in the fields of LbL assembly and gas separations. The compatibility of LbL deposition techniques with catalytic washcoating methods has not been explored in the literature to-date. Lastly, the durability and performance of LbL thin films have not been investigated under reaction environments or at elevated temperatures. Scientific results regarding each of these hypotheses are of substantial intellectual value to the separations community. Validation of the proposed coupling of catalytic and LbL polymeric films in a composite catalytic-permselective membrane will enable the rigorous development of an innovative approach to realizing low-cost, highly selective gas separation membranes. For the specific case of a water-gas-shift catalytic layer enhancing the permselectivity of a CO2-selective LbL film, recent theoretical predictions by Wilhite indicate that H2-CO permselectivities in excess of 250:1 (comparable to Pd films) may be achieved at roughly 1/100th the cost. By itself, this achievement could transform the field of hydrogen purification membranes. Planned outreach activities include mentoring of undergraduate researchers through the Department of Chemical Engineering's REU program and Engineering Scholars program. The PIs will also host an international research internship through the International Scholars Program at TAMU. Summer research opportunities will also be available to K-12 teachers through the College of Engineering's RET program.