(205d) Process Intensification Insights through Computational Catalysis Studies: Selective Ethylene Oxide Formation on Ag Catalysts

Process intensification (PI) is a design approach that leads to significantly cleaner, safer, and more energy-efficient process technology. Catalytic partial oxidation processes are responsible for an extremely large-scale industrial production, and also relatively expensive to perform. These processes typically operate at high thermodynamic inefficiencies because these catalytic reactions are very thermo-sensitive and also non-selective when even minor temperature excursions occur within the reactor. Thus, this industrial process is an excellent subject for PI studies. Herein, our studies focused on surface catalytic mechanisms of the ethylene oxide (EO) formation process. Periodic plane-wave Density Functional Theory (DFT) methods were used to analyze detailed reaction mechanisms comprised of elementary reactions on the Ag(111) surface facet with low coverage. Energetic changes of related species and pathways were calculated and will be discussed. DFT analysis is discussed in the context of microkinetic modeling techniques which provide detailed information on surface coverage and gas-phase species concentrations as a function of reactor process conditions and feed ratios. Key surface species have been identified to suggest the key factors for the selectivity during EO formation. Our results are consistent with previous kinetic modeling efforts in the literature which did not employ DFT analysis.¹ Lastly, our study demonstrates how fundamental theoretical investigations and multi-scale modeling techniques are currently impacting the advancement of rational catalyst design in the light hydrocarbon processing industry.

1. Stegelmann, C. et al, J. Catalysis 2004, 221 (2), 630-649.