Co-oxidation of Ammonia and Ethanol in Supercritical Water, Part 2: Modeling Demonstrates the Importance of H 2 NNO x JASON M. PLOEGER, 1 WILLIAM H. GREEN, 2 JEFFERSON W. TESTER 2 1 Aerodyne Research, Billerica, MA 01821 2 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 Received 21 January 2008; revised 25 March 2008, 26 March 2008; accepted 26 March 2008 DOI 10.1002/kin.20345 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A co-oxidation model was constructed from available submechanisms for ammo- nia and ethanol oxidation. The ammonia submechanism validated for combustion at atmo- spheric pressure conditions was modified for the higher densities and lower temperatures (655–700 ◦ C) of supercritical water. The ethanol submechanism had previously been tested and validated at supercritical water conditions. The initial model poorly reproduced experi- mental ammonia conversion data and was not able to consistently match nitrous oxide pro- duction as a function of temperature over a range from 655–700 ◦ C at 246 bar. To improve model predictions, the low-pressure NH 2 + NO x submechanism was replaced with a submech- anism that included the H 2 NNO x adduct species that are expected to be stabilized in the high-pressure supercritical water environment. Thermochemical and kinetic parameters for the adduct species were estimated with quantum chemical calculations using Gaussian 98 with Correspondence to: Jefferson Tester; e-mail: testerel@mit.edu. Contract grant sponsor: Army Research Office. Contract grant number: W911NF-05-1-0522. Contract grant sponsor: Shell Oil. Contract grant sponsor: Malaysian University of Science and Technology. Contract grant sponsor: Martin Family Society of Fellows for Sustainability. Additional information on stable species and transition states in NH 2 + NO 2 and NH 2 + NO submechanism, H 2 /O 2 supercriti- cal water oxidation submechanism, and molecular diagrams show- ing dominant species transition states in NH 2 + NO 2 and NH 2 + NO reaction surface are available as supporting information at www.interscience.wiley.com. c  2008 Wiley Periodicals, Inc.