Microkinetic Modeling of Ethylene Glycol Decomposition On Pt and Ni-Pt Bimetallic Catalysts

Tuesday, November 9, 2010: 4:18 PM
Grand Ballroom F (Marriott Downtown)
Michael Salciccioli, Chemical Engineering, University of Delaware, Newark, DE and Dion Vlachos, Director of Center for Catalytic Science and Technology (CCST), University of Delaware, Newark, DE

There has been increasing interest in the utilization of biomass for renewable energy and chemical production. Biomass, which is made up of oxygenated hydrocarbon building blocks, can be more efficiently utilized for chemical and energy production through the use of small-scale catalytic reforming technologies. Small-scale reactors can increase localization of synthesis gas production and increase reaction rates over current large-scale and enzymatic technologies. Distributed synthesis gas will allow for local production of methanol, ammonia, liquid fuels (Fischer-Tropsch process) and hydrogen for fuel cell applications. Recent technological successes in catalytic reforming of biomass derived oxygenates have shown high reaction rates and high product selectivity towards hydrogen for smaller oxygenates such as methanol, ethylene glycol and glycerol. Future improvements and extensions of this technology to larger oxygenates will require rational design for reactor and catalyst optimization.

Microkinetic models provide necessary insights into surface chemistry that are useful for reactor design and catalyst optimization. The focus of this study is the development of a thermodynamically consistent microkinetic model that describes the detailed mechanisms of thermal decomposition and reforming of ethylene glycol on a Pt(111) surface. A hierarchical methodology was implemented for refinement of sensitive kinetic parameters via DFT and allows for the inclusion of adsorbate-adsorbate interactions for abundant surface species. The surface mechanism describing oxygenate chemistry on Pt(111) includes over 100 reversible elementary reactions of the following classifications: adsorption/desorption, hydrogen extraction, carbon-carbon bond cleavage, hydrogen oxidation, carbon monoxide oxidation, hydrogen and carbon monoxide coupling reactions via the carboxyl intermediate, and oxidative dehydrogenation. Sensitivity analysis on rate constants shows that early dehydrogenation reactions are kinetically important.

Additionally, previous experimental research has shown that Ni/Pt bimetallic catalysts have increased activity toward oxygenate reforming compared to that of the parent metals. This work also explores fundamental descriptors for catalytic activity which explain the increased activity of the Ni/Pt bimetallic catalyst, and offers insight into future catalyst design for oxygenate reforming.

This presentation will focus on key model results and interpretation to reactor design applications and extensions of the model to other chemistry sets. A key focus will be on the mechanistic differences of the reforming of ethylene glycol on platinum compared to the reforming of ethylene glycol on the Ni/Pt bimetallic catalyst.

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