Atomic force microscopy study of the metal surface during a palladium- catalyzed hydrogenation membrane reaction

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Show simple item record Carson, Jared C. 2018-05-03T18:12:14Z 2018-05-03T18:12:14Z 2018-05-01 en_US
dc.description.abstract Characterizing a catalytic metal surface during heterogeneous hydrogenation is an enabling area of catalysis research. Available technology, however, often requires ultra-high vacuum or other limiting conditions which prohibit in operando research. Atomic force microscopy (AFM) can provide direct observations of fluid/solid interfaces at atmospheric conditions and in real time. Tapping-mode AFM can examine chemical and physical phenomena on surfaces in addition to topography. The work here describes using phase-angle information from tapping-mode AFM to observe liquid/solid interfaces in real time during the hydrogenation of styrene. Through optimized tuning and scanning procedures, it was possible to observe the onset of hydrogenation on the surface of palladium immersed in liquid in real time and with the topographic resolution inherent to AFM. This opens new avenues for in operando research on heterogeneous catalysis, a field that is of great fundamental and industrial importance. For reference, a catalytic membrane reactor (CMR) was used to observe the hydrogenation of phenylacetylene over a palladium layer as a batch process. It was determined that with a H2 diffusion rate of 3.7·10⁻⁹ mol/s and a theoretical, calculated H2 demand of at least 2.3·10⁻⁷ mol/s, the reaction would be hydrogen starved and would not progress at a realistic timescale for observation by AFM. By instead using either ethylbenzene (EB) or styrene (St) as the liquid in a solvent-free approach and injecting a small volume of the other liquid into the system mid-scan, the effects of changes in chemistry on tip-surface interactions were observable. EB injections in both EB and St-immersed scans showed no significant change in phase angle. Injecting St into an EB-immersed scan environment, however, caused an increase in phase which remained relatively constant for the remaining duration of the scan, demonstrating for the first time that a liquid-phase hydrogenation reaction can be observed in operando through the phase shift of tapping mode AFM. en_US
dc.description.sponsorship National Science Foundation National Institute of Food and Agriculture en_US
dc.language.iso en_US en_US
dc.subject Atomic force microscopy en_US
dc.subject Phase en_US
dc.subject Hydrogenation en_US
dc.subject Catalysis en_US
dc.subject Heterogeneous en_US
dc.subject Membrane en_US
dc.title Atomic force microscopy study of the metal surface during a palladium- catalyzed hydrogenation membrane reaction en_US
dc.type Dissertation en_US Doctor of Philosophy en_US
dc.description.level Doctoral en_US
dc.description.department Department of Chemical Engineering en_US
dc.description.advisor Mary E. Rezac en_US 2018 en_US August en_US

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