Studies of the Effect of Pressure in Membrane Reactors

摘要提案标题：膜反应器中压力效应的研究，提案编号：CTS-0622666，主要研究员：Ted S. Oyama，机构：弗吉尼亚理工学院和州立大学摘要：本项目涉及先进的膜和膜反应器的研究，以提高催化系统的性能，通过耦合的传输和反应过程。要检查的具体反应将是氧气辅助的甲烷自热重整制氢。这是一个有吸引力的反应，因为使用氧气允许放热燃烧反应和吸热重整反应同时操作，这导致有效的热利用。此外，氧气防止催化剂因焦炭形成而失活。我们最近开发的联合收割机无机膜结合了高氢渗透性（5 × 10-7 mol m-2s-1 Pa-1）、选择性（1500）、稳定性（500 h）和在高压和高温下的惰性，使研究成为可能。该膜是管状复合材料，由多孔α-氧化铝制成的基底支撑体和氧化铝基底的梯度层以及最上面的二氧化硅薄层（30 nm）组成。它们通过溶胶处理和化学气相沉积（CVD）的组合来制备。膜的当前渗透性超过纯Pd的渗透性，但我们将进行研究以显著提高渗透性。这将通过两种方式实现。首先，通过控制层的粒度和厚度来优化源自勃姆石溶胶的中间梯度层的孔径。第二，通过使用混合元素CVD来设计最顶层的成分。后者的工作将由从头DFT计算指导。我们已经成功地获得了激活能的分子通过模型硅环结构，匹配的实际渗透数据。我们计划对包括金属（Y、Zr、Ti等）在内的各种成分进行理论组合筛选，非金属（B、Al等），和镧系元素（La、Ce等）指导实验工作。自热重整的膜反应器研究将在高压（20-30大气压）下进行，并且将包括反应动力学的测量和用1-d（纵向）和2-d（纵向和径向）数学模型描述反应器。一个主要的目标是调查1-D和2-D描述之间的过渡制度，并制定标准的模型，可用于一般的反应的适用性。反应器研究还将探索以一种新的方式克服跨膜压降损失的可行性：通过利用反应本身摩尔数的增加。该项目的更广泛影响是巨大的。自热重整是能源化工领域的重要研究课题，解决了天然气的高效利用问题。二氧化硅膜制备的发展也将在其他领域如沸石或氧传导膜中找到适用性。这项研究将为研究生提供包括实验和理论方面的广泛学科的高级培训，以激发创造性思维。重要的是，将通过积极招聘，高度重视妇女、少数民族和本科生的参与。将与当地一所本科学校（拉德福大学）的一名教员开展实质性合作。促进个人的个人成长，并鼓励该校学生参加高等教育。

Abstract Proposal Title: Studies of the Effect of Pressure in Membrane Reactors, Proposal Number: CTS-0622666, Principal Investigator: Ted S. Oyama, Institution: Virginia Polytechnic Institute and State University Abstract:This project deals with the study of advanced membranes and membrane reactors for enhancing the performance of catalytic systems by coupling of transport and reaction processes. The specific reaction to be examined will be the oxygen-assisted, autothermal reforming of methane for producing hydrogen. This is an attractive reaction because the use of oxygen allows the simultaneous operation of the exothermic combustion reaction and the endothermic reforming reaction which leads to efficient heat utilization. In addition oxygen prevents catalyst deactivation by coke formation. The studies are made possible by our recent development of inorganic membranes that combine high hydrogen permeance (5 x 10-7 mol m-2s-1Pa-1), selectivity ( 1500), stability ( 500 h) and inertness at high pressure and temperature. The membranes are tubular composites consisting of a base support made of porous a -alumina with graded layers of a alumina substrate, and a topmost thin layer (30 nm) of silica. They are prepared by a combination of sol processing and chemical vapor deposition (CVD). The current permeance of the membranes exceeds that of pure Pd, but we will undertake research to improve the permeance significantly. This will be done in two ways. First, by optimizing the pore size of the intermediate graded layer derived from the boehmite sols through control of the particle size and thickness of the layers. Second, by engineering the composition of the topmost layer by using mixed-element CVD. This latter work will be guided by ab initio DFT calculations. We have successfully obtained activation energies for passage of molecules through model Si ring structures that match those of actual permeation data. We plan to carry out a theoretical combinatorial screening of a wide variety of compositions that include metals (Y, Zr, Ti, etc.), nonmetals (B, Al, etc.), and lanthanides (La, Ce, etc.) to guide the experimental work. The membrane reactor studies on the autothermal reforming will be carried out at high pressure (20-30 atm) and will include measurement of the kinetics of the reaction and the description of the reactor with 1-d (longitudinal) and 2-d (longitudinal and radial) mathematical models. A major goal is to investigate the transition regime between 1-d and 2-d descriptions and to develop criteria for the applicability of the models that can be used for general reactions. The reactor studies will also explore the feasibility of overcoming pressure drop losses across the membrane in a novel manner: by harnessing the increase in moles of the reaction itself.The broader impacts of the project are substantial. The topic of the research, autothermal reforming is important in the energy and chemicals area, addressing the efficient utilization of natural gas. The developments in the silica membrane preparation will also find applicability in other areas such as zeolite or oxygen conduction membranes. The research will provide advanced training for graduate students in a broad discipline that includes experimental and theoretical aspects so as to stimulate creative thinking. Importantly, great emphasis will be placed on the involvement of women, minority and undergraduate students by active recruitment. A substantive collaboration will be initiated with a faculty member from a local undergraduate school (Radford Univ.) to promote personal growth of the individual, as well as to stimulate the participation of students from that school in higher education.