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Conflict of Interest: In relation to this article, we declare that there is no conflict of interest.

Publication history: Received March 20, 2016
Accepted June 20, 2016

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Kinetic modeling and dynamic simulation for the catalytic wet air oxidation of aqueous ammonia to molecular nitrogen

Deuk Ki Lee^† Jeong Shik Cho Taejong Yu Yong Su Lee¹ Jae Wan Choe¹ Sang Soo Lee¹

Department of Fire Safety, Gwangju University, Gwangju 61743, Korea ¹Department of Civil Engineering, Gwangju University, Gwangju 61743, Korea

dklee@gwangju.ac.kr

Korean Journal of Chemical Engineering, November 2016, 33(11), 3109-3114(6), 10.1007/s11814-016-0175-6

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Abstract

A kinetic model for the catalytic wet air oxidation of aqueous ammonia over Ru/TiO2 catalyst was developed considering the consecutive reaction steps as follows: (i) formation of active oxygen sites O* by the dissociative adsorption of aqueous O2 on the catalyst, (ii) oxidation of aqueous NH3 by the reaction with three O* sites to produce HNO2, (iii) aqueous phase dissociation of HNO2 into H+ and NO2-, (iv) formation of NH4 + by the association of NH3 with the HNO2-dissociated H+, (v) formation of N2 by the aqueous phase reaction between NO2- and NH4+, (vi) formation of NO3 by the reaction of NO2- with an O* site. For each reaction step, a rate equation was derived and its kinetic parameters were optimized by experimental data fitting. Activation energies for the reactions (ii), (v), and (vi) were 123.1, 76.7, and 54.5 kJ/mol, respectively, suggesting that the oxidation reaction of aqueous NH3 to HNO2 was a ratedetermining step. From the simulation using the kinetic parameters determined, the initial pH adjustment of the ammonia solution proved to be critical for determining the oxidation product selectivity between desirable N2 and undesirable NO3- as well as the degree of oxidation conversion of ammonia.

Keywords

Catalytic Wet Air Oxidation Aqueous Ammonia Kinetics Modeling Activation Energy pH

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