Chemically sensitive imaging in heterogeneous catalysis – from microscale to macroscale

2009 Spring Symposium

 
Jochen Lauterbach
Department of Chemical Engineering
University of Delaware
Newark, DE


Abstract – We have been using high-throughput (HT) approaches based on rapid-scan FTIR hyperspectral imaging in the mid-infrared to screen catalyst formulations for the discovery and optimization of new and improved materials. In combination with HT methods, we also employ a variety of more traditional spectroscopic methods to understand the underlying fundamental science.

Two examples will be used to illustrate this research approach: de-NOx for automotive exhaust after-treatment and ammonia decomposition catalysts for CO free hydrogen generation.While HT screening is a macroscopic analysis technique, we are also interested in observing non-linear phenomena on working catalysts in situ on the microscale using spectroscopic imaging based on ellipsometry. The collective, global behaviour of a catalytic system depends on the effective communication of local reactivity variations to distant points in the system. One mode of communication occurs via partial pressure fluctuations in the gas-phase above the catalytically active surface. This gas-phase coupling mode is considered to be most effective under vacuum conditions, where the mean free path between molecular collisions is large. We take advantage of a spatially distributed system of isolated chemical oscillators to investigate the details of gas-phase communication in the 10-3 Torr range. Characterization of local gas-phase variations, in conjunction with local kinetic activity on the surface, shows that surface/gas-phase interaction might differ from the conventional assumption of a gradient free, molecular flow environment near the surface. This analysis provides a quantitative estimate of the effective gas-phase coupling length in a heterogeneous system. This coupling length was found to be in agreement with surface imaging results which qualitatively showed coupling between oscillators.

Speaker’s Biography – Jochen Lauterbach received his Diploma in Physics at the University of Bayreuth, Germany under Prof. J. Küppers and his Doctorate in Physical Chemistry at the Fritz-Haber Institute of the Max-Planck-Society, Berlin, Germany under Professor G. Ertl. He came to the US in 1994 with a Feodor-Lynen-Fellowship of the Alexander von Humboldt-Foundation and performed his post-doctoral work at the University of California at Santa Barbara under Prof. W.H. Weinberg. He joined the faculty at Purdue in 1996 and, in 2002, moved to the University of Delaware, where he currently is a Professor in the Chemical Engineering Department. His research interests include the design of catalytic materials using high-throughput screening methodologies and in situ spectroscopic techniques, development of catalyst synthesis methodologies based on microemulsions, nano-engineered polymer films from renewable feedstock, and non-linear dynamics of chemical reactions, in particular external spatiotemporal forcing. Professor Lauterbach has published close to 100 papers/book chapters and has given over 150 invited presentations.