CAREER: Designing Partial Oxidation Catalysts for Selective Gas Microsensors

Purdue University, West Lafayette IN

Investigators

Abstract

Abstract PROPOSAL NUMBER.: 0644707 PRINCIPAL INVESTIGATOR: Baertsch, Chelsey INSTITUTION: Purdue University There 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 Merit For 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 Impact The 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.