Lanny D. Schmidt, Associate Fellow

Two-Dimensional Reactor and Catalytic Radiant Burner Modeling Using Detailed Chemistry

High-temperature, short contact time catalytic reactors show great promise in many applications, ranging from the production of synthesis gas and olefins to catalytic combustion and incineration. These researchers studied the production of oxygenates and olefins from the partial oxidation of alkanes in a single-gauze reactor and the production of high concentration hydrogen syngas streams from partial oxidation of methane in monolith reactors with steam addition. This project focused on the detailed fluid dynamics and reaction pathway simulations associated with these reactors. The oxidation of cyclohexane over a Pt-10% Rh single-gauze catalyst was carried out in the laboratory. This process enables the exothermic production of an outlet stream that has an 85% selectivity to oxygenates and olefins at 25% cyclohexane feed conversion. Density- Functional Theory (DFT) with B3LYP/6- 31+G(d) method for geometry optimizations and thermodynamic analyses was employed using gaussian98 to predict reaction enthalpies and rate-constant parameters for this system. The major gas-phase reaction channels (29 species, 46 irreversible reactions) were probed by locating stable reactants, products, and transition- state intermediates; and one-dimensional simulations were carried out with chemkin’s plug program. These calculations gave qualitatively correct trends with cyclohexane/oxygen ratios and dilution. Related work focused on combining the gas-phase kinetics with surface chemistry and two-dimensional fluid dynamics in fluent to properly simulate the quenching and surface generated radicals associated with the system. These researchers also developed surface mechanisms for the partial oxidation of methane over Rh-coated foam monoliths. Fluent was used in combination with userdefined subroutines that enable surface/gasphase chemistry coupling to simulate twodimensional flow in a tubular catalytic wall reactor. This work focused on the further development of these surface mechanisms to explain the experimentally observed water-gas shift and steam reforming reactions associated with steam addition to this partial oxidation system. Fluent was used in combination with this refined mechanism to simulate and capture the complex interaction between heat transfer, mass transfer, surface chemistry, and gas-phase chemistry. Further research was performed in densityfunctional- theory modeling of cyclohexane partial oxidation in millisecond single-gauze reactors. Cyclohexane oxidation over a Pt-10% Rh single-gauze catalyst can produce ~85% selectivity to oxygenates and olefins at 25% cyclohexane conversion and 100% oxygen conversion, with cyclohexene and 5-hexenal as the dominant products and cyclohexanone a minor product. Understanding the favored reaction pathways suggests ways to adjust reactor operation for desired product distributions. Detailed numerical simulations of the surface-assisted gas-phase process allowed the investigation of experiments, which are often costly or potentially dangerous to carry out.

Research Group and Collaborator

Gregg Deluga, Graduate Student Researcher
Olaf Deutschmann, Heidelberg University, Heidelberg, Germany
David Henning, Graduate Student Researcher
Dimitrios I. Iordanoglou, Research Associate
Abhishek Jhalani, Graduate Student Researcher
Emil Klein, Graduate Student Researcher
Jakob Krummenacher, Graduate Student Researcher
Corey Leclerc, Graduate Student Researcher
Ryan P. O’Connor, Graduate Student Researcher
Mike Pawson, Research Associate
Jeremy Redenius, Graduate Student Researcher
Razima Souleimanova, Research Associate
Srinivas Tummala, Research Associate
Karthik Venkataraman, Graduate Student Researcher
Ed Wanat, Graduate Student Researcher
Kevin West, Research Associate
Christy Wheeler, Research Associate
Kenneth Williams, Graduate Student Researcher