CAREER: Designing Partial Oxidation Catalysts for Selective Gas Microsensors

AbstractPROPOSAL号码。当前迫切需要能够检测和量化多组分气体混合物中碳氢化合物和挥发性有机化合物浓度的微传感器，用于环境、健康和安全应用。新的传感器将需要实验室规模分析工具的精度和准确性，但同时必须低成本，低功耗，快速响应和便携式。目前适合携带的微传感器不能提供足够的化学选择性。使用传统的微传感器技术（如半导体气体传感器），在定义良好的气体系统中，只需要由100个传感器组成的阵列来实现适度的化学特异性。提出了一种新型的催化微传感器，它只需要一个本质选择性传感器，就可以为特定的、定义的气体分析应用提供高达100%的乙醇选择性。选择性乙醇微传感器的应用范围很广，需求量很大，包括分析可再生液体燃料、汽车废气和炼油应用中的污染监测，以及用于疾病检测的呼出气体。对于特定的工艺应用（包含有限和确定的气体混合物），化学特异性将通过使用纳米结构金属氧化物催化剂来实现，其表面经过调整，可以在多组分气体混合物中选择性地氧化所需的分析物。由放热部分氧化反应引起的温度变化将使用微热传感器来测量，以将选择性事件转换为定量浓度。这种传感方法新颖而优雅，原理简单，可以通过调整催化剂衬底来应用于广泛的过程。具体来说，将开发含有小VOx、MoOx和WOx结构域的过渡金属氧化物催化剂，用于在碳氢化合物和挥发性有机化合物混合物中选择性地将乙醇氧化为乙醛。利用成分、纳米结构、催化剂活性、反应机制和表面性质之间的关系，混合金属氧化物催化剂将被设计成对产物和反应物具有期望的特异性。已经证明，使用VOx-Al2O3催化剂，乙醇可以在180℃优先氧化为乙醛，而不发生苯或甲烷气体在多组分碳氢化合物原料中与空气的反应。催化剂、动力学和微系统设计协议在多组分混合物中选择性氧化乙醇所需的基础发展将使这种传感器方法推广到更复杂的气体系统和应用中。广泛的影响利用催化传感机制和复合氧化催化剂的选择性化学传感器的发展将产生一个全新的研究领域。这项研究将为催化传感器的开发提供基础设计方案，并为需要乙醇分析的特定过程应用提供实际设备。利用我们的微加工方法在催化剂表面集成测量能力，将使我们能够以前所未有的方式在新的水平上探测表面现象。通过这项工作，研究生和本科生将在催化和微系统的界面上进行新的多学科领域的研究和课程。女性和少数族裔高中生、本科生和研究生将受益于PI正在进行的指导/推广工作，包括讨论女性在工程领域令人兴奋的机会以及平衡个人和职业目标的方法的研讨会。

AbstractPROPOSAL NUMBER.: 0644707PRINCIPAL INVESTIGATOR: Baertsch, ChelseyINSTITUTION: Purdue UniversityThere is a critical need for microsensors capable of detecting and quantifying the concentration of hydrocarbons and volatile organic compounds in multi-component gas mixtures for environmental, health, and safety applications. New sensors will require the precision and accuracy of laboratory scale analytical tools, but at the same time must be low cost, low power, fast response, and portable. Current microsensors that are suitably portable do not provide sufficient chemical selectivity. With conventional microsensor technologies (such as semiconductor gas sensors), arrays comprised of 100s of sensors are required to achieve only modest chemical specificity in well defined gas systems.A new class of catalytic microsensor is proposed that only requires one intrinsically selective sensor to provide up to 100 % selectivity towards ethanol for specific, defined gas analysis applications. Applications for selective ethanol microsensors are broad and in demand, ranging from analysis of renewable liquid fuels, exhaust gases from automotive and refining applications for pollution monitoring, and exhaled breath for disease detection.Intellectual MeritFor a specified process application (containing a finite and determined gas mixture), chemical specificity will be accomplished by using nanostructured metal oxide catalysts with surfaces tuned to selectively oxidize only the desired analyte in multi-component gas mixtures. Temperature changes resulting from the exothermic partial oxidation reaction will be measured using microcalorimetric sensors to transduce the selective event into a quantitative concentration. This sensing approach is novel yet elegant in its simple principle and can be applied to a wide range of processes by tuning the catalyst substrate.Specifically, transition metal oxide catalysts containing small VOx, MoOx, and WOx domains will be developed for selective oxidation of ethanol to acetaldehyde in hydrocarbon and volatile organic compound mixtures. Using relationships between composition, nanostructure, catalyst activity, reaction mechanisms, and surface properties, mixed metal oxide catalysts will be designed with desired specificity towards products and reactants. It has been shown using VOx-Al2O3 catalysts that ethanol can be preferentially oxidized at 180 C to acetaldehyde without any reaction of either benzene or methane gases present in multi-component hydrocarbon feeds with air. Fundamental development of catalyst, kinetic, and microsystem design protocol required for selective oxidation of ethanol in multi-component mixtures will allow the generalization of this sensor approach to more complex gas systems and applications.Broader ImpactThe proposed development of selective chemical sensors using catalytic sensing mechanisms and complex oxidation catalysts will generate a completely new field of study. This research will lead to both fundamental design protocols for the development of catalytic sensors and actual devices for specific process applications requiring ethanol analysis. Integrating measurement capabilities at catalyst surfaces using methods characteristic of our microfabrication approaches will allow us to probe surface phenomena at new levels and in ways previously never envisioned.Through this work, graduate and undergraduate students will do research and take courses in a new multidisciplinary field at the interface of catalysis and microsystems. Women and minority high-school, undergraduate, and graduate students will benefit from the PI's ongoing mentoring/outreach efforts, including seminars discussing exciting opportunities for women in engineering and methods for balancing personal and professional goals.