Mechanical Engineering Graduate Seminar

Abstract

Basic chemical insights are needed to support the transition to energy-efficient chemical transformations such as heterogenous catalytic oxidation and plasma-assisted processes. This presentation highlights the basic concepts of our mass spectrometry approaches to study the reaction networks in these complex environments and applications.  Using this technique, unprecedentedly detailed chemical insights are generated as it allows for the simultaneous and sensitive detection of all intermediates and products of the reaction network without prior knowledge of their identity. In the first part of the talk, we will highlight new insights into catalytic oxidation conversion of methanol near atmospheric pressure using near-surface molecular-beam mass spectrometry. In addition to a variety of stable C₁-C₃ species, we detected methoxymethanol (CH₃OCH₂OH), a reactive C₂ oxygenate that had been proposed to be a critical intermediate in methyl formate production. Methoxymethanol was observed above Pd, Au_xPd_y alloys, and oxide-supported Pd. We explored temperature and reactant feed ratio dependencies of methoxymethanol generation. The results suggest that future development of catalysts and microkinetic models for methanol oxidation should be augmented and constrained to accommodate the formation, desorption, adsorption, and surface reactions involving methoxymethanol. The second part of the talk highlights the chemical insights into plasma-assisted chemical looping combustion of simple hydrocarbons by CuO/NiO using low-temperature plasmas in a heated fixed bed, coaxial, double dielectric barrier discharge (DBD) reactor. Through time-dependent species measurements by an electron-ionization molecular beam mass spectrometer, we obtained chemical insights through the quantitative detection of intermediate and product species at various temperatures and plasma conditions. We observed considerable enhancement of fuel oxidation from the plasma discharge at lower temperatures. At more elevated temperatures, a period of carbon build-up was observed when using NiO as an oxygen carrier.

Bio

Dr. Nils Hansen is a physical chemist at the Combustion Research Facility of the Sandia National Laboratories in Livermore, CA, USA. He received his Ph.D. in Physical Chemistry at the Christian-Albrechts-Universität Kiel, Germany. Before joining Sandia in 2004, he worked as a postdoctoral researcher at UC Santa Barbara and as a staff member at the BASF AG, Ludwigshafen (Germany). Hansen’s research focuses on gas-phase chemistry that is relevant for energy conversion processes. He has dedicated his career to mass spectrometric detection and quantification of key intermediates in reaction networks using advanced mass spectrometric tools, making significant contributions through his research, innovation, and practical insights. Throughout his professional journey, Nils Hansen has garnered widespread recognition for his exceptional achievements. He has been recognized as a Fellow of the Combustion Institute and a Helmholtz International Fellow for his groundbreaking work, underscoring his expertise and influence in the field. He has delivered keynote speeches, participated in panel discussions, and conducted workshops at renowned conferences and events worldwide. He is a member of the editorial board for the “Proceedings of the Combustion Institute” and is the past-organizer of the biennial “International Workshop on Flame Chemistry” series. Nils Hansen has an impressive track record of collaborating with leading academic institutions, and research organizations. His collaborative mindset and interdisciplinary approach have fostered groundbreaking partnerships that have driven advancements in chemical transformation.